I was always brought up to respect police officers. In that situation, you follow their fucking directions. It's simple as that.

While I will disagree with your second point, I agree with this one. If the cops knock on your door and ask nicely then don't be a dickhead because you could end up being charged with more offences (in relation to assaulting police...etc). IMO people should watch what they do around the cops and be respectful of the fact they're not emotionally involved or trying to fuck you over... they're just doing their job of enforcing the law.

However, running up to a cop saying "get away from my son" is not a right you have

Who says so? I've told a police officer to 'go away' before because the circumstances were such that I didn't think his presence was appropriate. He refused, so I called the police and his boss ordered him to stand down. If the police really are doing the wrong thing, then I don't see any problem with politely asking them things like:
- Do you mind if I record this?
- What's your name and staff number?
- Why are you here today?
- Do you have a warrant?
- Can you wait a minute? I'm just going to call legal aid and check whether this is all above board... I've never had any problems with the police so don't know the process. My son's not going anywhere and I have no issue with you waiting outside for him, but I want some legal advice before you go barging in here.

IMO there's no reason why police should have to use excessive force, or go beyond their investigative powers in order to make an arrest. An arrest can be quite a calm and respectful experience from both parties. IMO 1/2 the problems arise when red-blooded cops charge in aggressively, swear at people, assert that they can do whatever the fuck they like and start using excessive force when somebody would have voluntarily come with them for questioning if they'd been less aggressive in their approach.