Havent watched the video so take with a grain of salt, but my guess is liberals seething that their totally effective and rebellious peaceful means of "resistance" are once again being called out for what they are. Ineffective, neutered, and whitewashed acts of whining that basically amount to spicy parades.
I want to also emphasize I am not against peaceful protest, but I do have a problem with people delusionally thinking its the end all be all and that peaceful protests have to be civil. I feel like the only merit peaceful protests really have, particularly the undisruptive kind, is to get people active. Its a gateway and foot in the door to get people onto the streets. But after that, there needs to be some kind of escalation because the powerful dont listen until it starts being disruptive.