"... I'm not sure how the Constitution doesn't equally apply to their protests."

This is because you're as dumb as a rock. 

The Unite the Right protester came to Chaerlottesville to demonstrate against statue removal in a park. They even went so far as to get a permit to do so, though their right to peaceably assemble isn't conditional on that. 

The antifas came to Charlottesville to violently attack the Constitutional rights of the first group.

The difference is obvious.