Why do cops allow this?
Because they are parasites too. Sucking up a paycheck, benefits and retirement while popping donuts and sucking down quarts of coffee. Then when you protect yourself from dirtbags, You get arrested and charged, because you have a income and assets they can tap into to keep their retirement fund in the green.
Chances are their political bosses ordered them to stand down and allow it.
Because the Dems who run the city sign their paychecks and ordered the cops to allow it.