Let me answer your question with a question: Why do -YOU- insist on attacking it?
Cause I have a boring internship, a lot of free time and free internet?
Well partially... cause I can't stand people ignoring facts
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Let's go trouhg this slowly..
Now, we are TOLD that the Old Gods slumber imprisioned and the darkspwan seek them out and corrupt them.
We KNOW that the tainted (and only the tainted) hear the old gods call. This establishes a clear connection between the Old Gods and the taint. How? Why? Good questions and this raises many suspicions.
Is the Archdemon really a corrupted Old God? Is it really slumbering defencelss? What if it's calling the darkspwan to corrupt him on purpose? What if it's allready corrupted and just called the darkspwan to wake it up? What if it's the source of the taint? What if the archdemon as we see it IS the original Old God - in apperance and behavior? Why is it's soul somehow connected to the taint?
Food for thought.
Now, the only things we know about the ritual itself is what Morrigan tells us, and that is little. She's highly evasive with the details and there's no way to confirm anything she sez. She did not show concern for children trought the game, so her assurances that the child will be unharmed sound hollow (especially given her definition of unharmed).
She does tell you that in these early stages of the childs development, the old god essence can be absorbed without destroying it. At no point does she say the child doesn't have a soul. In fact, from her ords, it's more likely that the souls will merge or something.
Some have raised the issue of the child having the warden immunity to taint. This is no where confirmed or even hinted.
Either way, we know so very little about how this ritual does and how it works, that almost the only thing we have to go on is Morrigans word. This is blind trust.
So at one side we have the sacrifice - proven way to end hte blight for good.
On the other we have a ritual we know nothing about, with unknown chances of sucess, that involves a/your child merging/being possesed with the essence of the oldGod/Archdemon (and yes, I use the term as one becase we dont' really know enough about the archdemon), with Morrigna leaving with the child to raise it as she sees fit, disallowing you from EVER seeing the child.
Best case scenario - Morrigan teaches the God child to be good (fat chance) and the child hepls fight the blight.
Best for some (let's call this neutral?) - Or she uses it to destroy the Circle or the Chantry (fat chance - most of the world is the Chantry , so it's be Morrigan and child vs. half hte world) This isnt' really a good outcome, givne that many would die.
Worst case scenario - Morrigna lied to you. The childs original soul is destroyed/ the shild is possesed, the God baby unleashes destruction upon the land or starts a new Blight.
So yea...given everything, taking the ritual is very naive/stupid and shortsighted at best, and downright selfish and despicalbe at worst. And everything in between.