This was a Critical Mass event, which is why the bicyclists are taking up all of the street as a way to reclaim the streets and protest the lack of safety for riders under usual conditions. It’s not legal, but protests are never useful if they’re fully legal now, are they.
If you’re so drunk or stupid you don’t realize you shouldn’t drive right into what is clearly an organized parade or protest, you need to have your license taken away. You are not responsible enough to be allowed to ride a bicycle, let alone drive a vehicle.