Those white nationalists are rare and dont represent conservatives!
This liberal idiot kicked a women! The entire left is unhinged sjw antifa
It's... a lot more complicated than that. First off, I don't think anyone who isn't a rabid loon thinks that the ENTIRE left supports things like Antifa. But the problem is that the left has become fractured thanks to the actions of people like this with the effective mentality of 'you either agree with this far left agenda or you're goosestepping through the streets and desiring to round up jews and gays into camps for gassing'. Since a lot of people on the left either don't agree or don't agree to the extent or... well... a lot of things, they fall into the latter 'category'. So if you're on the left but, say, think Trump isn't the spawn of hell incarnate and Hilary (possibly Bernie as well) was an awful candidate... you're flat-out 'vile'.
The thing is that this behavior is reinforced within the left with things like the media more than willing to champion the cause and stories popping up frequently of things like republicans being driven out of fast food joints and the like simply for, well, existing. When these destructive people pop up on the right the right is usually swift to condemn them and distance themselves from them. When they pop up on the left they end up having articles that are basically 'peaceful protesters drive out fanatical alt-right group'. Hence the difference.
People have more common sense than you think ---
If they drag you through the mud, it doesnt change whats in your blood