I don't think many liberals actually say that. Certainly here in Oregon they have killed different races & mentally ill people, and often unarmed or poorly armed & this is a relatively liberal state overall. So I think it's more about disprotionality & being often harassed more than whites in many areas. Some whites would react exactly the same as blacks in the same circumstances. It could be kinda racist & inferring that blacks, etc are inferior due to their reactions. I did not realize this very well until we had a black lady stay with us--the difference is very real, but there are large differences in the degree of it.