It's as though Ennis might see "being gay," rather than a tire iron, as being ultimately responsbile for Jack's death, so that it could increase his own internalized homophobia--his own hatred of "being gay."
I think this is a very astute observation. I've always considered Ennis's internalized homophobia a (relatively) bigger impediment to his happiness than his fear of being subjected to physical violence for being "gay". I think the same might well hold true for his emotions surrounding Jack's death.
Another event that I was wondering whether might have had the same effect - ie. increasing Ennis's internalized hatred of "being gay", seeing it as "wrong" or "bad" - is AIDS. Just a very few years after Jack died, Ennis could hardly have avoided the news stories; - the media and medical "frenzy" about the illness and the focus on how gay men in particular were affected.
Ennis wouldn't regard the illness in a Conservative Christian light, he's hardly a fan of the fire-and-brimstone crowd's views. But I've wondered if he might still not, influenced by the IMO far-less-than-balanced news coverage back in the day, consciously or subconsciously use it as fuel for the fire of his own "hatred of being gay": Might he consider it some sort of confirmation that his sexual orientation is "wrong" and "dangerous" and so increase his self-hatred. If it did have that effect on him, it might have served to send him further into that self-destructive behaviour (mainly drinking) that has been discussed in this thread, and so have pushed him further towards the passive form of suicide.
(I think I need a stiff drink myself after writing this. It's an interesting and worthwhile, but very depressing subject.)