I have good and bad news.
Good news: there's a whole Phd thesis, now published as a book, that deals with violence in Bukowski's prose work. As a phd it was called "Anatomy of Violence in Charles Bukowski's novels"(I love that title), now it's called " Tales of Ordinary Violence". I read it, it's actually quite good! Here is the amazon link:
Bad news: It's only in French ^^
I have it at home, and though it does not specifically focus on male to male violence, there are some interesting ideas you could use. For ex. I like how A. Thiltges makes use of psychoanalytical concepts for this topic.
You can have a look at the content on the amazon website. If you don't know French, maybe have someone giving you a hand.