Dem primaries are competitions and the candidates aren't all the same and it's good to air out their differences and it's good that noisy assholes on the internet yell at them when they are bad.
It just is not the case that if you mention that bad things TRUMP WILL WIN. It doesn't work that way.
Because of the internet and how they are covered more people are in tune with the minutiae of politics than they used to be. But, really, while now we have people yelling at strangers on the internet, the actual candidates seem to be much nicer to each other than they used to be. 1992? Nasty primary. 2000? Nasty primary. 2004? Nasty primary. 2008? Not actually that nasty. 2016? Not nasty at all.