"well... one criticism of homosexuality is that if everyone were homosexual, we'd have a hell of a population growth crisis on our hands."
If everyone were male, we couldn't make children. If everyone were white, racists wouldn't have anything to complain about. If everyone were disabled, we might actuality have to spend money building ramps. That argument is so beyond ridiculous that nobody with sense could reason it in good faith. Everyone isn't. Some people are. If you want to think that those people are going to spend eternity suffering, I can at least understand your logic, even if I think it's terrible. In fact, we could totally make kids if everyone were gay. It's just so far beyond a non-issue.
"You are allowed to accuse someone of racism, sexism, bigoted and all of that, you are allowed to say racist, sexist and bigoted things: but you can't be vitriolic?"
No, you're not allowed to be bigoted. You're allowed to call it out respectfully if you get to it before we do. We punish bigotry and we punish vitriol.
I don't know that I'd classify American conservatism as *fundamentally* racist/sexist/whatever, but there are a lot of ideas pushed by the conservative establishment that do push those views, and I think that was true even before Trump (though in my opinion, he exacerbates things). There's a definite risk of normalization if we aren't criticizing these things, so that has to be allowed if we're having any political discussions, but generalizations and vitriol are both unfair and unproductive. The key here, as to everything, is balance.
As for Islam, there are undoubtedly issues in the Muslim world. There are extremists, as there are everywhere, and there are corrupt states hiding behind skewed interpretations of the religion to impose ridiculous standards and maintain power. That's not a condemnation of Islam at all.