Poly, I think talk to your T about this. I agree with you that it sounds like your friends experience has triggered your own process about your experiences too.

Try not to feel bad about that. Maybe just focus on your friends stuff when you're with him, but ensure you make space to work through yours with your T. Could you have extra sessions at the moment?

Maybe running, working out, journaling, painting etc will help you work through your own anger until you see your T.

I guess your anger was going to hit at some time, so it's good that it's happened when you have a T who can hopefully help you through this.