The officer mentioned in the full video that Falter had been walking directly against the protest and wasn't just trying to cross the road like he claimed. Which, "openly Jewish" or not, is a good reason to stop him, I think - for his own safety and the safety of the people in the march. And coupled with the fact that he very visibly is Jewish, it makes his actions seem a lot like a counter-protest - something the police generally try to limit or contain regardless of the protest subject.
The police officer had the patience of a saint, honestly. He offered to escort Falter to the place he wanted to go via a different route - so as to avoid the protest - probably around a dozen times. It's very clear Falter didn't really have any intention of getting to his claimed destination.