Ummm, who said it was illegal to tape them?
You can tape just about anything that happens in public. You just can't interfere with them while they do it.
As to the punch, I don 't have a problem with it. She had no right or reason to shove him. I think he showed restraint in just giving her one. She retreated and he went back to dealing with the original one. I think he should have been a little more aggressive with her so he could get her under control faster.
I don't care if male or female, adult or juvenile. At the time you put your hands on a cop (or anyone for that matter) you open the door for bad things to happen to you.
Here is a good tutorial related to police encounters...