Quoth our dear leader, "There is no justification for violence against law enforcement."
A cop once told me that in some places basic arithmetic is an opinion. And cops can never be wrong. So, if the certainty of basic arithmetic is contingent upon location, I see no reason why the certainty of the above declaration by our president should not be as well. Therefore, the claim that nothing justifies violence against the police is, just like basic arithmetic, an opinion in some places.