I’ve had a few ideas why they might act like that. Perhaps it comes from a place of shame? They get horny over it but due to how they’ve developed negative views on LGBT+ people they feel disgusted or ashamed with themselves and then feel compelled to then go on a crusade against “le gays” as a form of projection, to prove that they aren’t “one of them”. Mean think of all those times people who’ve been pretty outspoken in their anti-LGBT views only to later be caught having seen a bunch of guys on Grindr or been identified at a gay orgy or something, feels like a meme at this point.
Maybe its from paranoia that they’ll be caught out and think if they’re the ones that shout the loudest against them, then people won’t think theres a chance they are LGBT+, which could have pretty devastating consequences for them where being found out could lead to social ostracism, or at least the perception thats what would happen.
Or perhaps its just pure opportunism and they don’t really care about if its consistent or not. Hell they might not actually have any actual hatred towards them but do so because it will get them more votes in an election where a sizeable section of the electorate are quite bigoted or to get invited to give talks, write books, make a podcast, etc. Hate is a strong emotion and be exploited quite effectively in the right places if you’re looking to make a profit.
Now I wouldn’t say thats an exhaustive list of all the potential reasons why people might still go on to be bigoted to LGBT+ people despite their hornyiness towards them, cus theres probably about as many possible reasons for that as there are people out there, but theres a few theoretical ways I could see how it might happen.