Yes, they understood each other, and disagreed, fundamentally. To the point where they seperated from each other. Knowledge and understanding =/= peaceful coexistence. For that you need something akin to the Heretic Virus. ANd that's for a races that shares perspectives.
Wow. Is it really that difficult to keep things in context? This is like the up-tenth time you've failed to view it within the context of the argument.
Fact: The geth understood one another and were at peace. Fact: When they separated and turned on one another they no longer understood each other.
I never said they had no disagreements. I said they understood each other. You can understand someone without agreeing with them. The geth understood the heretics and did not think they were wrong. Legion's own words clarified that. Neither result was an error. They were still understood and accepted.
The context of this was elaborating how when the geth remain together and understand each other, there is peace between them. When they lose that understanding, there is conflict. This was to put emphasis on the fact that with true understanding there comes peace. It all tied back to the context of why synthesis would bring peace due to it bringing a new realm of understanding.
For the geth, for as long as they understood each other, there WAS peace. That is the lore. Don't like it? Doesn't change the lore. In the lore for as long as the geth understood each other they were at peace, unity. Yet when they break apart and eventually get in conflict with one another, guess what happens? The geth can no longer understand the heretics. This is not my assumption or theory or wild headcanon. It is the lore.
Well as far as I'm concerned, you shouldn't have to go to outside sources to understand what's going on in the freaking game. And indoctrination doesn't just go away. Just because the Reapers stopped speaking to kenson doesn't mean she was no longer indoctrinated: she was. SHe was simply bereft because she was left alone without her new gods.
You don't. The indoctrinated and husks still retaining their original selves is partly in the game and in other part all pointed to in the game. The novel only clarifies the husks. We already knew it about indoctrination thanks to Benezia specifically and to lesser degrees TIM and Saren. The bit about the husks was never directly told in the game but there is elements of the lore that support it being the case. What with the harvest being preservation. Aswell as the mind being something preserved in reapers already, and other cases of this being possible in the lore in other areas that I rather not delve into.
I didn't say Kenson wasn't indoctrinated. The point was that it wasn't a persistent indoctrination that kept her on that line of thinking. At the end, since the reapers severed the signal, while it was still technically indoctrination it was indoctrination at that point in the same sense us humans can indoctrinate people to believe the earth is flat. There was no longer a present indoctrinating force behind the scenes edging her thoughts in one direction. She wasn't no any longer directly under any influence of theirs, she just still genuinely believed all the wonderful things they told her.
This is unlike Saren and TIM who were constantly being influenced by reapers until the very end. Near the end for Kenson, when the reapers terminated the signal and she lost the connection, she still believed in them not because they were forcing her to because she had been genuinely swayed to their side due to the promises of wonder and splendor or whatever crap they whisper in her ear at night. Maybe they cuddled her and told her sweet I love yous, I don't know.
All this does is further elaborate my point on how indoctrination has various functions. Not all indoctrinated servants are struggling to control themselves and fighting for control. Not all are completely under the control of the reapers. It varies. It's a very powerful tool with a lot of versatility.
Coincidentally I find your argument of not wanting to accept outside LORE into the story a bit amusing considering how many times in the past you've referenced completely unrelated material from outside sources in your attacks on the ending.
But at any rate, you're assertion seems to be that if only people can have the "truth" beamed into their heads along with the proper context to understand it, everyone would ract to it the same way. I say that if such was teh case, you are not teaching, you are indoctrinating. No two people absorb information the same way.
Its less my assertion and more what synthesis puts forth. Also, theres only one way to view the information within the context of synthesis. That is why they all come to the same general conclusion, which doesn't involve war and hate and bitterness. Just like the geth. The geth did view things different from the heretics but they still understood and accepted them. There was still peace. It was only when they separated, grew distant and lost their understanding of one another did conflict arise.
With understanding comes peace. Comes acceptance. Comes harmony. Thats the utopia synthesis brings. Kumbaya...
But what you are cramming into the person's brain here isn't laws of gravity or aerodynamics, or physics. Scientific principles that can be demonstrated with repeatable experiments. You're cramming your own version of philosophy and a very subjective perception of ethics and "perfection" and declaring it the only True Path To Enlightenment.
The reapers are preservation of life. The reapers are alive. The reapers represented salvation from an inevitable extinction and disaster. These are tangible facts in the lore. That is the story. With synthesis we'd now understand that fully and completely, we'd understand how they're alive and why it was necessary. That those harvested before are still with us. What used to be life that we couldn't comprehend or accept is now simply that - life. We're all one now.
You make it sound like there should be a philosophy argument of "what is life?" to be had here. There isn't. In synthesis, it IS life. We are all the same. The whole point about the ending is that there won't be any line between organic and synthetic anymore. We're all alive and we understand each other. To say "well, some might not view reapers as life" or what-have-you would be akin to saying "nothing is living". We're all the same form of life now, we've all been given a new framework. Though the glory of The Shepard. It's a magical experience.
The situations are very similar in my mind: In both cases are being used to "correct" someones wrong-thinking in order to end conflict. To change his thoughts. Dorian already understood the reasoning behind the arrangement; Tevinter had been practicing this for centuries. They are attempting to breed a better quality mage: one that embodies all that Tevinter values. They are trying to reach, in their perspective, the final evolution of human life. And Dorian's father was trying to make him see and understand that. With blood magic.
Mainly due to your misunderstanding and refusal to look at things within the appropriate context. They're not the same. One provides you with understanding and perspective. The other just forces someone to accept a view point. At anyrate I rather not continue talking about Dragon Age. In the same way you don't like Mass Effect lore dragged into a Mass Effect conversation if that lore comes from an official lore novel, I don't like talking about the lore of a completely different type of game in a Mass Effect context. I don't know Dorian, I don't care about Dorian. All I know about the situation is what you have told me, and if that is what the situation is then it isn't comparable to synthesis. The fact that you think it is only shows your own misunderstanding of synthesis or a misrepresentation of what is happening with Dorian.
best way to make sure the reapers aren't around anymore is to pick destroy
Cheers to that. It's also significantly less complicated. Shepard lives, reapers destroyed, victory. 
Yes the fact that the Reapers are still around and free to do whatever they want is the most obvious downside of Synthesis. I'd prefer if more people at least hated against this actual downside instead of hating against Synthesis because of their headcanon mind-control theories or "no individuality any more" nonsense, which reveals either a disquieting inability to understand simple vocabulary or a complete disregard for the epilogue.
Honestly the rational that people should hate on actual problems rather than headcanon ones is something I'd apply to all the endings, not just synthesis. I agree nevertheless.
Well, obviously. I don't think anyone is arguing against that.
IT believers might. 
All-in-all, I think I'm done here. I've said all I feel like saying about an ending I have so little care for. Though I hate synthesis due to its horrible execution and methodology rather than the actual concept behind it. That I can get behind. As it stands however its just too magical. Tossing someone into a beam of light and magically changing all life in the galaxy, right down to the trees, into synthorganics... I'm done. I'm just done. I like the general idea (minus the ALL life bit, leave the trees alone) but the execution was cringe worthy and very out-of-touch with the lore.
Besides, most of the discussion in this topic is kinda like....
Point
Head