Maybe but there's many black Americans that openly bash gays, especially in rap (although that might have cooled down idk) and while some Christians definitely are hard against them, I'd say most either don't care or disapprove but still treat them with respect. Having said that, black Americans are only 13% of the population and Muslims, who alot also are not a fan of them, are an even smaller group so you could very well be right about SCM's being the most common doing it. Having said that mouthful, it seems only WSCM's get the backlash, that I've seen.
You could say that about every group tho. There are laws that legally discriminate against whites and Asians, affirmative action for higher education. Both Asians and whites are under represented in universities and college, despite having the top average sat scores, with a few possible exceptions, Jews being possibly one although they are WAY over represented for being 2% of the population.
Regardless, that's the only systematic racism I see. Then you have hiring practices that favor minorities, women and LBGT over straight white males, so I would disagree that only the LTBG community are discriminated against. London police: No SWM need apply. CBC news in Canada (Like the BBC as a national broadcaster funded by the government) : No SWM need apply. Openly announcing it as a hiring practice. I'm sure there's more but I'm blanking. At least an Asian group is suing Harvard for discrimination.