...because violence is a core value of liberalism.
Remember Liberalism Rule #3: "We know better, and thus the ends justify the means.". This is the rationalization being used by your party (and I hope not you as well).
I seriously hope you will leave the progressive movement, but I am afraid that you are so invested that it might prove more than you are willing to do.
Trump and R's make mistakes...you don't have to always agree. But the Left has been co-opted by evil.