This is good news. The lesson here is that even in left-liberal strongholds, where the authorities are SJW-amenable, it is both legal and prudent to prepare oneself for violent confrontation with antifa and Black Bloc. As long as your preparations are primarily defensive, and your actions are in response to the Left's violence, there is a reasonable chance that the authorities will refrain from doing more than attempting to put a brief scare into you. So hit back twice as hard.
Their reasoning is pretty simple, I suspect. If people cannot defend themselves with open, obvious, and limited means, they are going to start defending themselves with concealable and lethal means, and if they are prevented from doing that, there is a very good chance they will start engaging in reprisals that are considerably less easy to witness or prevent.
US society is observably on the decline towards primitive and tribal standards. One common aspect of primitive societies is ritual limited violence. This would appear to be a natural step towards that, in line with tattooing and body-decorating.