Occam's razor applies. Trump's a racist.Regarding the Trump shithole comments...
It can be seen as Trump saying what a lot of people are thinking, which has always been part of his appeal. There are going to be plenty of Americans who like what he said, and some conservative defenses of a more nuanced view (just as there will be liberal attacks on the implications.)
It may cause significant political damage because while some mostly white people may think he was right, they might not going to be as motivated by the comments as the international community, or immigrant groups in the United States (as well as anyone who thinks his comments are about race rather than, say, education level of the typical immigrant).
It's troubling because an individual's character or ability to contribute to the United States is not determined by where they came from. That's not really a conversation his administration wants to have, while trying to get legislative support for immigration moves.
A lot of the coverage suggests that it's an effort to motivate the base, but this wasn't something Trump issued as a statement to the public. It was part of a conversation with lawmakers, which is a different context (He could've been saying something he knew would get out, or it could have just been his views/ advocacy for his base.)