I agree, this is a really difficult balance. In the real world I think Tyler would have said "Ok, I'll try and be nicer to those other folks" during the one-on-one meeting then returned to his original behavior w/in a matter of days or weeks.

So, do you compromise the technical strength of the team by firing Tyler or do you compromise team unity by keeping him?

My thought is that this is not a simple one way or the other answer. The post took the middle ground of talking with Tyler, which I don't think would really work out the way he wrote most of the time. Is there something else he could have said?

If you've had several conversations and this behavior is just the way it's going to be then what are the boundary conditions around when it's best to keep Tyler around vs firing him?