“Is there some reason that you don’t think that the name-calling schtick from the leftists isn’t harmful to the democrats?”
Because I see no indication that it has done so. Maybe it won’t hurt Trump either - but IMO it feeds directly into the “likability” issue that the left has relentlessly hammered him on, and I think he inadvertently continues to give them fuel...which in turn can influence undecided voters who are too stupid to see past it and focus on issues. I think that calling her what she is (radical leftist/socialist) is effective, but if he gets into the schoolyard memes it starts working against him.
And nice guy President Bush finished his term with the lowest approval rating for a president in the 20th century.