Gold, Loghain is a monster and needed to be put down-you don't coddle a mad man. You eliminate him.
He's a resource. Nothing more, nothing less. Whatever he may or may not have done in the past is irrelevant. That is at the very core of being a Warden. Having one of the finest military leaders of the day - though he might have many other flaws, his prowess as a commander is undoubted - on your side will increase your chances of stopping the Blight. To not accept his help is to unnecessarily risk the lives of everyone in Thedas. If he needs to be eliminated, that can be done after the Blight is over.
Right,Mages made Templars tranquil for little or no reason.. Mages beat,murder and raped Templars.
The Templar thugs couldn't wait to rush out to kill mages, the tranquil, and everybody they thought was a mage.
Some Templars act like that. And some mages run around abusing their powers. Hell some mages use blood magic to rule over a slaveocracy. And in the book in question, some mages are perfectly willing to kill innocents for no reason other than to frame the Templars while some Templars act against their leadership to help people.
Templars are thugs that got by with anything because the Seekers always blamed the mages. Cassandra said the Seekers failed to see the problem.
Some Templars are thugs. Some care deeply about their charges. Some are in it to take advantage of their position. Some are in it because they believe they are keeping the people of Thedas - mage and non mage alike - safe. (Hey, it's almost like the police in America - some of them are decent folk, protecting the public, others are abusing their position to inflict violence on people....)
Under those conditions I support the mages.
Supporting the mages is a reasonable position given the abuses inflicted on them by some Templars. Of course, so is supporting the Templars given the abuses of power we have seen from some mages.
I rescue the Greys and recruit them into the Inquisition since they was under mind control and some was fighting against the ritual at Adamant.
Good choice, they are a useful resource. On that has to be watched for signs of corruption, but one that can be used none-the-less.
You have to take in the whole picture and make a solid decision based on the facts. Again the thugs refused to talk at Val Royeaux and again when you speak to the Lord Seeker on Cassandra's quest.
Yeah, the "thugs" refuse to talk, while the mages have willingly sold themselves into bondage to a bunch of slave owning blood magic users who are clearly involved with who or whatever caused the breach. Not exactly paragons now, are they?
You certainly do need to look at the whole picture. And the whole picture is this: both sides are deeply flawed. And even beyond that, at the point where you make the choice in DA:I, the real big picture is the hole in the sky. Everything else pales in comparison to that. You should side with whomever you feel is best suited to helping close the Breach (and there are arguments both ways). Nothing else really matters.