The thing that any "voting against their best interests" critique misses is that most people are willing to vote "against their best interest" if they feel like it's the morally correct thing to do.

Like, I'm an adult who never intends to have children, but I still support robust public education. I could make some arguments about how paying taxes for schools is somehow in my best interest. But the reality is I support public education because I think it's the right thing to do, not because I think it will personally benefit me.

The thing is, conservatives and Republican voters don't lean that way because they're just too stupid to vote for Democrats. It's because they have a different moral framework. And that's something that can be hard to reconcile and address. Changing someone's political views requires changing their entire worldview, which is incredibly difficult.