“Poverty shouldn’t exist” or “unemployment shouldn’t exist” is much better rhetoric than “billionaires shouldn’t exist.” It’s positively framed instead of antagonizing. 

And that’s exactly why nobody ever says those things.

Think both approaches have issues. 

"Billionaires shouldn't exist" is thrilling to people already sold on socialism/communism but alienating to everyone else. 

"poverty shouldn't exist" sounds nice but is so generalized that it means little.

IMO. "Freeze the rent" and "Free Busses" were much more effective because they're tangible. But we're now in the general and he is going to need to walk the line of firing up his base + winning people deeply critical of socialism and his proposals. Right now he seems to be mostly focused on firing up his base (which is the easier thing to do).