We all know the GOP elites are horrified at the rise of Trump. They want you to believe their revulsion stems from outrage over issues but, if you dig a little, eventually you realize that's only the surface of the story. They don't like Trump because they don't understand his success, can't control him, and don't know what he'll do if he manages to win.
He's a wild card and, as I've said before, there's nothing your "political betters" hate more than unpredictability. When things go off the pre-determined rails, these people have to actually pick sides, make decisions, and stand on principle. That's all such a bother.