The same question applies to you. Well?
You're assuming that the plain clothed people getting out of plain cars did the "standard things that police would do", with no justification for assuming that.
You seem to be insisting that the police can do no wrong
I'm pointing out to you that the police have become their own worst enemies; that their behavior can and does often look criminal.
If the police want to be respected, they need to show some respect. That might reasonably start with looking unmistakably, unambiguously, like police. Plain clothes and plain cars arethe polar opposite of this.
“You’re assuming...”
No, I’m not. You’re assuming they didn’t. I am not assuming either way, I just pointed out the assumptions you have made.
“You seem to be insisting that the police can do no wrong ”
Nope again. They certainly can do wrong, but you seem to be assuming that they definitely did wrong, without much evidence either way.