Trump proves to be a science denier (anti-vax, anti climate change) which is a bad start for a president. Also, a president who thinks that mexican immigrants all want to rape american women is not what america wants.
1) The U.S. president can be considered the figurehead or "face" of America. Trump is not a suitable person to represent a whole country. 2) A country should not be run as a business, and it seems this is his intention. 3) His ideas for foreign relations would ruin U.S. ties with other countries.
He only sounds good to the uninformed. He complains about Mexicans? Net immigration from mexico last year was 0. He said i'm going to remove Obama care and replace it with "something terrific" wow such policy much president. All he says is words and half of them don't make sense to any thinking man.
That's a catchphrase based on your belief. You need to provide specific examples and arguments to back that up. You can't just throw that vague nice-sounding phrase down as if that proves a point.