Things must have changed since I lived in San Francisco starting around 1975. I didn't find the brothers self-loathing, but I have noticed when I go on forums in general, that the way people talk to each other is pretty nasty. Not my experience before the Internet.
However, I think there will always be people who don't like themselves, and given that Blacks are only 12% of the population, it would seem that there are just as many White gay men who don't like themselves. Truth to tell, I found that to be more the case, and I lived there until 2002.
Self hate starts early in life, before you're even 5. Nature/nurture plays a big part in how we grow up - or don't grow up. The easiest way to tell if you like yourself is simply how well you respond to a compliment: do you say "thank you," (non-self hating) or "Yeah. Right." (low self-esteem)? If I encounter a guy and pay him a compliment, whether it's just someone I know casually, or someone I'm interested in, that response alone tells me whether or not I can enjoy the person's company or if I'm going to have to fight through his self-protective defense mechanism (and I don't waste time doing that anymore. At 64, the remaining part of my life will spent with those who can enlighten my consciousness). Einstein gave up on the human race towards the end of his life because he thought mankind gave up on itself, and lost its capability for remaining curious (therefore, open to learning). When people only know facts and, in a conversation (or many conversations) spout nothing but "information", and are not sensitive to others, there's a good chance they're not happy with themselves. I always translated, "Thou shalt love thy neighbor as thyself," as "if I don't like myself and can't be kind to myself, I certainly can't genuinely care for another person and be kind (most of the time) to them." Sounds like you're meeting a certain type of brother. You might consider what environments you're frequenting that you're running into this type of brother. When I was growing up in the 60s, we had an expression, 'he's an angry Black man." I guess that's coming back, huh?
Where were you (which part of the West Coast, since you didn't say) that you encountered what you say you observed?