I would say it was because they weren't black killed by a white person, but they seem to have forgotten pretty quickly a real racist leftist killed black people several times.

It's the authority figure part they want to rebel against, specifically the male authority figure. Daddy wasn't in their lives, so they need something to tell fuck off and hope they die. Even the rich ones with both parents, but neither were present to raise their spoiled little cunts. They hate daddy because white male cops represent daddy to them, the symbol of ultimate authority.