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.
one could very well argue that it’s still your fault if you hit someone who unexpectedly jumps out, if you cannot stop in time for such a thing you are driving too fast.
It’s like sprinting right past a corner and then insisting it’s not your fault when you inevitably run into a person who walks out from behind the corner. You fucking slow down when approaching a place like that, then speed back up when you are not longer liable to hit people.