I see what you mean and I am a survivor of massive trauma so I'd be the friend in this scenario.
Let me explain how I see it, as it is a thing.
If I have been disciplined by having a hand around my throat and my head being banged backwards repeatedly against the wall, that memory is present in me for a long time and it is going to influence my feelings about having normal conflict in non abusive adult relationships. I'm going to avoid that conflict as much as I can, run away etc.
Shouting can upset people, stonewalling, mud slinging arguments - all can be incredibly damaging and the survivor has to wade through their own personal response to that to come to zero ('I no longer mind conflict') let alone come to a positive position about conflict ('I can handle and get something positive out of my conficts'). At the moment, your friend is feeling conflict as it has damaged him, and now you feel his response is damaging your friendship and how you can behave around him and what you can say.
As the traumatised person in healthy relationships, yet again I am on the back foot because everyone is functional now except me, and I've got my little bits left to resolve, if I ever will - so thanks again, abusive childhood - it is not nice to be that person when normal people don't understand and judge us, and we know we don't handle it right but we just can't help it, it is hard wired in me to be aware of people who might get so angry with me that they bang my head on the wall by my hair. I don't want to upset them and I just want to get away to safety by myself.
If your friend is in therapy or not, he may have some way to go to be comfortable in conflict and until he is, you may see strange or different behaviour, as you describe. It's like the ripples that spread out from abuse (yet another reason why abuse needs dealing with.)
Can you try not to see it as so much of a problem? Can you ask, when he is feeling better, what goes on for him and why? Do you know much about what happened to him? Any airing out will help him I expect.