
No! NOT COLE!

In fact that is exactly kind of thing Cole will do.
If you're truly an a*shole, he will be angry about it but he won't turn into a demon to punish you for what you did. He will just be disappointed and walk away.
Dorian, you mean? He and Cole honestly would be great friends! Blackwall seems a bit of an odd choice but considering how kind he seems, he and Cole would be natural friends! Never thought of that.
Here is my guess:
Solas, Iron bull, Cassandra, Dorian are written by Patrick and David, so they won't be mean to Cole.
Both Blackwall and Cole can hear the song of Old Gods, they have something in common.
Varric is a funny and reasonable guy, so I guess it won't be a problem.
Looks like Sera has some serious issues with demons, but she has a soft heart. I will bring Cole during her personal quest to test if it's possible to bend on her attitude to Cole.
Vivienne won't get along well with Cole, they are not the same kind of people.