He is the embodiment of greed, ambition, bigotry, and dislike of the marginalized. Of course, all that means is that he simply instantiates in a clear way the values of the GOP, but they don't like those being so out in the open! Trump is in fact the very product of what Republicans stand for: he's a monster they created, but now they don't like it. They want those values, but expressed sotto voce, and by a slicker candidate.