Well he is a bit of a Christian fundie so that kind of goes hand-in-hand with homophobia. He's also just generally an all-round certified douchebag who has at some point managed to piss off just about everyone in the metal industry. He's also, coincidentally, a conspiracy nutter. He's such a monumental twat that I feel bad any time I buy one of their albums (old megadeth albums kicked serious amounts of ass, musically speaking).
As for death and black metal bands most of the ones I follow are too busy with norse mythology and general fantasy bullshit to bother saying anything homophobic lol. I do know though that the earlier black metal scene had a lot of assholes in it, as well as a few figures who were more than a little messed up.
Should probably mentioned too that the singer of Gorgoroth is gay (he's also among the messed up memebers of the black metal fraternity, so the messed up ones aren't always homophobic too lol) . But he's the only openly gay member of an extreme metal band that I can think of off the top of my head.