This is one of the dudes in NYC that tries to take off illegal license plate obscurers on cars, including (and typically) cop cars, since they’re very often used (illegally) by law enforcement.

I don’t really have anything to add other than that this didn’t seem like a violent action. He may not have even known those were secret service and assumed they were undercover police cars. The general point of his and others that do this is that it’s illegal but cops seem to do it without any punishment, and it makes it harder to identify and report cops that park illegally, drive recklessly, commit criminal behavior and drive away, etc.