I keep reading the thread title and interpreting as a question on whether Fred Phelps is a
p-zombie.
On topic, I'm relatively sure at least some of them (Fred being the most obvious) do it for the money & attention. But that doesn't mean he doesn't believe it. In fact, he probably does, which is why he chose this particular means of shit-stirring.
Also, there's evidence that simply publicly speaking in favour of an idea makes you more likely to believe it. Assuming Fred was even slightly homophobic at first, by now he must be as hateful as he acts.