Welp, the far right doesn't give a toss if you're in favor of peaceful solutions. They'll gas or lynch you regardless.
And if the law won't protect left wing protesters from the right what choice do they have but counter-violence?
The far right doesn't. But the people who are more on the fringes and might have sympathies--but still have a conscience--do care. So when they see people on the left being peaceful, they realize which side they want to be on, but when both sides are violent, they stick with their original gut feeling, and the far right grows.
And, again, the left CANNOT let it come to violence. They cannot win in that scenario. If the image of the conflict becomes one of two violent factions, that will doom the left, because when it comes to violence the right will always beat the left, plus the right will gain sympathy because of the "violent leftists" attacking them. The left must be nonviolent or they cannot win the larger battle of ideas--and anyway, when you resort to violence, you're admitting that the only way you can get someone to admit to the correctness of your ideas is to beat them into it or kill them (in which case their opinion becomes irrelevant); essentially, an admission that you can't win in the realm of ideas.
Antifa is the single greatest gift the left could ever have given the right, because it undermines everything that the left stands for and undermines the case the left makes for its ideas, and justifies violence from the right in "self-defence."
The left cannot start the violence and cannot allow the debate to be settled by violence. If either is true, the left will lose.
And there's a key difference between WWII and now--WWII was a matter of foreign policy, while what's going on now is a domestic conflict.