There is the root of the problem. Why should a person allowed to enforce laws when he is ignorant of the law? It is absolutely insane to provide "qualified immunity" to law enforcement officers for being unqualified to performed their duties.
And, in this specific case, I sincerely doubt the officer was ignorant of the law. I suspect he just wanted to exert his "power" over a person who dared to behave in a non-sheep-like manner while in his presence.
Police have computers with internet in their cars, so there is noexcuse for being ignorant
SCOYUS recently ruled that cops can make up law on the spot.
I am not defending the cop here but as was said in an above post the laws are “voluminous and vague”. No one can know all of them at all times. I am not excusing the actions of the cop and there should be repercussions for him. I am basically saying that there are too many laws.