That's a bit of an extreme and somewhat irrelevant example, and seems to be written to suggest that anyone sworn at by a police officer is definitely in the wrong, or being extremely abusive themselves.
But I assume from what you've written that in some circumstances you deem it okay for police officers to be rude and abusive towards people. So that gives some clarification at least.
On that basis, to keep on topic, that presumably means it's hardly a big deal if members of the public do it.
I should have, yes. However, I was intimidated and decided not to. Said officer had said he'd arrest me and was right up in my face to 'go away'. I know he wouldn't have been able to arrest me for offering to help witness an accident, but if he did, and his colleague played along then who knows what grief I'd have had?
I wouldn't walk away now, for what it's worth.