I might be wrong but I've not heard him say anything that is racist. No doubt there are some that are supporting him because they're racist, that doesn't mean all are. On that note I would love someone to prove me wrong and show me a clear example of Trump actually being racist.
I'm a conservative Christian. As a conservative, the left look down on me and assume there is only ignorance fueling my world view. There are issue like abortion, that to me are like the holocaust. I know most don't agree with me on that, and I can understand that they don't see a fetus as a life, I get it. But imagine for a second that you were firmly convinced that a fetus was as much a life as a new born. Things like that will drive you to vote Trump despite hating some of his actions.
The left also treats Christians with disdain. You have to get people on side if you want them to vote for you. Not tell them they're idiots.
While I don't agree with them some see gun rights as fundamentals to their freedom. You can't just tell these people were going to restrict guns, you have to get them to believe that it's for the best. Not tell them they're idiots. Then call them racist sexist bigots when they don't vote your way.
Immigration in the states is not in a good way, having so many people living illegally is not good for anyone. Trump might sound harsh but at least he is willing to tackle the problem (even in a way I'd not go for).