The President doesn’t control the police, except for Federal cops like the FBI, the DEA, and NPS rangers. Municipalities control and fund their own police forces, as do the states. The protesters may not like the President, but there is very little that he can do about the issue that they are protesting about because he simply doesn’t have the power because of Federalism. He can’t tell local cops what to do. Of course a lot of people on the left think that the government is all one big thing because they don’t really understand how it works. Leftists that do have a clue want there to be one big central powerful government, but of course someone like Trump or worse could be in charge of that.