A rational person can seek a compromise with people they view as idiots. A rational person cannot seek a compromise with people they view as evil.
That logic can only go so far, if you are dealing with attitudes and actions that are in every way wrong.
If I say "the sky is blue" and you say "the sky is red", you don't really have much to compromise about. Similarly, if one individual says "All people should be treated equally", how exactly do you compromise on that point? "You are treated equally but only on weekdays, weekends we can still discriminate against you"? That's the way it is with things like gay marriage (opposed by religious groups).
But the bigger barrier is the general attitude of people on the left that require ideological conformity to the point where it is not enough for a libertarian to agree with the left on gay rights or immigration they are still evil if they oppose higher minimum wages or affirmative action. There is much greater diversity of thought on the right than on the left...
No, there really isn't.
Yes, there are people on the left who have a set of core values that they think people must follow. But there are also people on the left who have no problem picking and choosing which ideas to adopt. And consider all of the Trump supporters who even attack republicans if they should speak out against some of Trump's actions.