>>535305406
Ansur was right. When you become a mindflayer, the "you" ceases to exist and it's replaced by the mindflayer. It's not usually a transformation where you retain your sense of self like depicted in the game, it's a complete consumption of the host which is used as fuel for the production of the mindflayer. Under the normal rules, Ansur was 100% correct. His friend was already dead, and he was just killing the monster that ate him.
Also, if you were becoming a mindflayer, your friend giving you a quick death would be a mercy.

However, bg3 changed the nature of cermaporphosis, and some characters throughout the game retain their sense of self. They explain that the netherese nature of these tadpoles changes all the rules, but it's unclear if this aspect was intentional or a story concession, since the player character suddenly losing control of their character wasn't something they wanted (even though that would be kino from a realism standpoint).

It's worth mentioning every time this comes up that there actually is a prophecy in illithid culture about an illithid who retains their sense of self after transforming. It's called "the outsider", and it's a doomsday prophecy that is supposed to spell the beginning of the end for their species, so it's interesting that the Emperor (and Karlach, and Tav, and Orpheus) all fit the description of this prophecy. I wonder if Larian was digging deep and referencing this esoteric piece of lore, or whether it was an accident and they were just doing their style of ceramporphosis where the person is still themselves.