a story of patriotism...

What a surprise , Haplo the troll popped up with nothing to say about the topic in question.

Darkside.
It really is a simple issue.
You keep going on about rights, that shows you donn't understand the law.
Your father had issues with the opinion of the council official, that shows he doesn't understand the law.

When you choose to go into a council meeting the only rights you have there are those the council says you have.
The only opinion on what is acceptable conduct in that meeting is the person whose job under law is to decide what is acceptable conduct.

The whole issue is that your father didn'tunderstand the law and didn't realise that the word of that "pesky official" is the only word that counts.

That is why he was arrested and charged with trespass(unlawful presence in a municipal building to be specific).
He gave up his right to freely wave his flag and to say what he likes the moment he walked into the meeting.....
It really is that simple, its very basic law.
From the moment that your father refused to do what the official told him he was commiting an offence.
Under Dutch law the official (who has no powers of arrest) is then obliged to call the police.