Need to take a hard look at the effect of brain washing to make any sense of that one. Why anyone, no matter who they are, would think a symbol of racial hate would make them look better.
In truth a police officer is an employee of the state. They can't wear anything that shows affinity to any belief, preference or party. This covers anything they could wear or within or on their vehicle. There have been officers fired in the past for refusing to abide by these rules.