It's definitely true that white collar, urban liberals sometimes punch down at rural, blue collar white people. It does hurt them politically.
I'm having trouble seeing anything Trump says about anyone other than high-level elected officials as punching up though. Attacks on the sitting president are punching up by definition, but the challenger always does that.
It seems more to me that he's telling people who don't feel good about their position in society that there's someone below them. That was the message of slavery, of apartheid, and of Hitler. I find it hard not to condemn those who were receptive to it.
Not many, and those who come to mind weren't receptive to that kind of messaging. Reasoning I've heard includes "Biden ruined the economy", "vote R no matter who", and "RFK and Tulsi Gabbard endorsed him".
The statements I've heard from Trump himself are "illegal immigrants are going to steal your job, the election, and your cat", and "trans people want to fuck your kid", which are about groups of people with very little political power.