Oh boy... If this is the kind of advice we're giving our visiting spotter-friends, the regular Amsterdam spotters may face a very interesting spotting situation in the years to come:
If you are sent away for no good reason:
* be polite and respectfull but defend your civil rights
* ask the motivation for sending you away.
* tell you are on public roads
* ask the id and name of the officer
* write down name, id number, car license plate and time
* Make photos or film the event or ask other to do so. You are allowed to film police officers on public roads.
* tell you are sending a complain
Just listen to the law enforcement officers. Even though you are on public terrain and you may not do anything illegal, just leave when you're asked to. And submit the complaint afterwards.