Whether I help a PERSON in trouble depends on the person. If he's a cop, that changes little.
We had a decent young Deputy around here for a few years; some of us kept an eye out for him. If we saw the vehicle but not him, we looked around to make sure he was OK. This guy we would unhesitatingly help.
We had a total psycho Deputy here for a few years; we kept our rifles close and watched who came to the door. If this guy was in a fight, most of us would ask the other guy if he needed more ammo.
There are many cases of citizens helping cops. Back in the day, cops were automatically considered Good Guys, and it was the Right Thing to Do. I recall the "Deer Hunter" being written up in the American Rifleman years ago, because he unlimbered his .243 when a convict was getting the better of a Texas Trooper at a rest stop, and put a permanent end to the problem. The DPS gave him a presentation Smith & Wesson. When one liberal Prosecutor made noises about charging him, a great many men in uniform told that Prosecutor there was no LEO in all of Texas who would arrest the man.
That was then, this is now. Two things to remember:
By actual body count, ten times as many innocent bystanders are killed by police as by non-police good guys.
The absolute Ultimate Crime today, far worse than rape, robbery or murder, and for which Prosecutors have NO mercy and cops are utterly Savage in their enforcement, is Doing the Job the Police Believe is Theirs.
I'll make my decision based on what I know of the parties. Just because someone wears a uniform does not make him a good person, or the guy shooting at him a bad person. OH, and if they are wearing black armored Ninja suits and have lots of fancy black weapons, I KNOW they are terrorists.