With Rice, the cop who killed him was literally offered another job as a cop.
With Garner, did you not see the people who said that the fact that he could say "I can't breathe" was proof he could, in fact, breathe and did not suffocate? Or the political pressure on the coroner to rule his death not a homicide? (Which, to her credit, she refused to do.)
With Castile, what was probably most infuriating is that he did everything right: he told the cop he had a gun, he showed the cop the gun, and he still died for, essentially, exercising his Second Amendment rights while black--and the NRA, that great defender of gun rights (which worked with Reagan to enact California's gun restrictions after the Black Panthers marched into the state Capitol armed, when any number of white groups had previously done so), was silent on the fact that a legal gun owner was cut down in cold blood by a cop (and don't try to tell me they wouldn't have been raising hell if Castile had been white).
And as for Martin, look at the reaction in parts of the media. The focus wasn't on the guy who killed Martin; it was on how Martin did drugs and was a bad kid and such, as if that somehow mitigated what his killer had done.
White people do not, by and large, get treated the same way black people do in the US, in life or in death. White people's lives matter more than black people's lives.