Because it is blatantly offensive to my mind that the gays have such persecution and are seemingly ignored by other minorities like blacks, when they themselves were oppressed just as much, simply because conservative Christianity is popular among the black population.
The Church was certainly implicit in the enslavement of blacks in the first place, they need to understand how their struggles are the same, or they're as guilty of the same, "It's not me, it's not my problem" mindset that white people had when it came to the abolition movement or civil rights.
In other words, just because some black people don't think the two are the same doesn't make them right, it makes them wrong.