Let me just say, that while the perception is the reality, my reality is at odds with that.
I live in a traditionally red state, GA - and in the north part of the state - think Appalachia.
I like to think I'm selective about who I'm friends with, and the large majority of my friends here are Republicans, and don't much care for Obama. Maybe 1/3 of them are supporting Trump and the rest, like me, have not yet decided what to do on election day.
But, significantly, none of my friends are stupid. None of them are crazy. And none of them are racist. Most had hopes for Obama when he won, though I don't think any voted for him.
Unless one invokes some sort of "No True Scotsman" fallacy, at least in my world your assertion about that "huge percentage of Republican primary voters" is incorrect. I think you paint with too broad a brush.