Being questioned by police and detained by police are two different things. It went from questioning to detaining in a split second for virtually no reason.
LOL!!!
First, you are not required to answer any questions offered by anyone, even the police.
If the police are conducting an investigation, they can lawfully detain you in order to question you in concert with the investigation.
Prior to that questioning, you MAKE them arrest you and then you should receive what is called the Miranda Warning:
"You have the right to REMAIN silent. If you GIVE UP the right to remain silent, anything you say CAN AND WILL be held against you in a court of law. You have the right to an attorney. If you cannot afford...etc."
It seems like the only course of action the man could have taken was to apologize to the officers for dancing in the street and say he was going to go home. This however would have been to accept that you do not have the freedom to dance in the street - which we do. In a residential area, it is perfectly legal to dance or do many many many other things on the street - none of which warranty a call to the police, or to be forcefully arrested and placed into a squad car.
The police are called to a scene, having received a report.
They are required to report to that scene.
I know you want a world where the police just ignore all that, but that really isn't how it works.
You have an idea of what does and what doesn't warrant police investigation and/or intervention and I'm sure you realize others have their views about it also.
This wasn't just a case of police "doing their jobs". They put their hands on him, when there was no sign of danger, no sign of threat. And the man didn't even try to resist by any means other than words.
The police can put their hands on you or anyone else.
So can I or anyone else.
There are consequences to that action.