I absolutely agree the abortion is the big divider. It's hugely important to a large group of conservative voters, and many of them are single issue voters on abortion. It's why Roy Moore is probably going to win in Alabama.
I'd put guns up there with abortion. Not quite as high, but high enough.
I also agree that same sex marriage sort of feels settled. Younger conservatives especially, I think, have mostly accepted this if not agree with it. The battle now is over things like do you have to decorate a cake for a same sex wedding that you object to. But that will all be sorted out. And interestingly, and importantly, culturally the populace was ahead of politicians and the courts when it came to same sex marriage. I think that's a big part of the reason that once things started happening, they happened quickly. The public's acceptance to gays and lesbians has grown dramatically in just the past decade.
The thing is though, even if I disagree with conservatives on abortion and same sex marriage, I don't automatically assume the worst about their intentions. I don't assume that a pro-choice person is a misogynist who wants to enslave women. I don't assume that someone who believes marriage is between a man and a woman is a homophobe who hates gay people. If someone says they want a secure border I don't assume they're a xenophobic bigot. If they're pro-gun I don't say they have blood on their hands everytime there's a mass shooting.
That's not so say that some of this is not rooted in sexism, or racism or homophobia. There's no doubt some of it is. But I also think there are people who, for religious or cultural reasons, feel differently than I do in good faith. I might think they're wrong, but that's different than attacking their motivations. And that's what a lot of them hear on social media all day. Even if you think they're a racist because of the policies they support, it doesn't mean they think of themselves that way.
There was an interesting study recently regarding how conservatives and progressives define things like racism differently. Conservatives tend to think a person is racist if they act with some kind of racial malice or bigotry in their own lives, whereas progressives tend to regard someone as racist if they support what they regard to be racist policies. It's an interesting distinction and that I think explains some of all this.