"Clarence" isn't in fact a joke directed at gays, it's directed at people who put them down. At least that's how I'd understand it, and I've met the man who wrote it.

Of course, it might get sung by someone who didn't understand it and was singing from an anti-gay point of view. That kind of thing can happen to songs easily enough "Born in the USA" for example, and I'm sure we can all think of other examples.

Here's a link to the song in the DT