"Sorry, but the kid began the exchange confrontationally for no reason whatsoever. You don't have to be a "cop worshipper" to see that."
And he was all set up to tape it, too.
In my area, the police MUST notify the public of DUI checkpoint, in advance. I believe they have to give the date and street.
If that was the case here, I expect this 19 year old went out to find, provoke and tape the response he got.
The cops didn't handle it too well, either.
I'd say both sides had a bit too much attitude that night. And both have tapes to show nobody got clobbered, handcuffed, beat up, detained for hours.
For the cops, the question is not helpful. Might as well just start with "have you been drinking?"