Well, when I suggested that class, not race gave rise to the higher proportion of African Americans polling hostile to gay marriage, I was drawing on some experience.
Twenty years ago, in Britain, the government brought in legislation to prevent the promotion of gay relations as equivalent to heterosexual ones (Clause 28 of the 1988 education act). The trigger was a promotional booklet used by the municipal authority where I was working at the time, Haringey Council. As this thing blew up into an hysterical campaign that was hotly contested all around the country, some of us who worked at the council organised opposition to Clause 28, and I ended up being the chair of the 'Haringey Council Workers Against Clause 28'.
Our particular brief was that we wanted the workforce to commit to oppose Clause 28 (on the assumption that the council leaders would duck the fight). So for around six months I spent most of my time trying to get Haringey's municipal workers to rally to the cause of gay rights. It was not impossible, and if anything, I thought that the council were too conservative when it came to asking their own workers to support them. But at the same time, you would have to say that most of secretaries, clerks and refuse workers we tried to win over were not spontaneously sympathetic to gay rights. Nor did I find that black workers were any more sympathetic.
As for some less anecdotal evidence, I think you will find that Ronald Inglehart's 'postmaterial values' model - problematic as it is, anticipates that working class people are likely to be less liberal on moral questions, and I believe
The World values survey does not give a class breakdown on its question, how many of you think homosexuality is never justifiable, but it is pointed that it skews according to the degree of development in the country. Also Chris is right, ex-Eastern Bloc countries are intolerant. So 81 per cent of Albanians think homosexuality is never justifiable, 78 oer cent of Lithuanians, 96 per cent of Zimbabweans, but only 25 per cent of Britons and 32 per cent of Americans.
On Chris's southern connection point, I am not so sure. Didn't the greater part of the northern migration of African Americans happen between the world wars? That would make most black Americans at least two generations away from the old South.