yes yes...so what do they do about it?

This cop should have done nothing because he wasn't equipped or trained to do anything about it.

If you're instead trying to deflect away from the fact that this cop violated policy and the law to skip the judicial process and become the sentence, well that's just sad.

If you are so concerned that you want an answer for how to deal with large groups of bikers misbehaving, then you take a look at the different policies put into place for how to approach these things. Typically the police will show up with sufficient manpower to block the entire roadway, issue citations to everyone and have a bunch of flatbeds ready to haul off the bikes to the impound.

But this officer didn't have any of that, so he should have not done a damned thing about it except call it in on his radio.