I've engaged in these antics, so I can attest that they do happen.
I've gotten away with alot when badgering and heckling police officers. I've only been arrested once for this behavior. I think that the pigs are taken aback by people actually yelling at them. It might help that I'm a white male.
I never think about how my actions or behavior will play with the NLG types. I'm engaged in free speech, so isn't that what civil liberties lawyers are supposed to be for? What's the point fo free speech if you don't use it liberally?
Liza makes a good point about yelling drawing a crowd. That's one reason why you yell at cops.
I happen to think that people who yell at cops for mistreating protesters are wasting their breath, especially if they are yelling because they are shocked that the cops are acting violently.
The best reason for yelling at the pigs is to exercise your free speech rights. That's the dangerous thing about people who take free speech seriously. They start yelling at the pigs. If more of yelled at the pigs, it might create even more space for free speech.
Who knows, you might bum out a few cops into quitting the force.
Chuck