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.
The bikes in the oncoming lane are safe? C’mon what kind of joke. Blocking streets is one thing but they’re actually moving forward straight on in oncoming traffic, in what world is that safe?
In the world of every parade that has been performed in every major city for the last two centuries at least.