That's misleading. They are being recorded while they are being violent within the peaceful protests. They are being arrested when they leave because Feds don't want to disrupt the peaceful protests - so they arrest them when they leave the area. I have watched a few videos of this happening and all of them have the person in not just all black but also with a helmet, tools to break windows and baseball bats.

Here's one example where the dude who got arrested has a helmet on. Why's that needed in peaceful protests? Also note the thing he has on his left side. That's an attachment to break car windows:

https://twitter.com/greg_doucette/status/1283452585945583618