It is interesting that you are calling a petty criminal like Rayshard "the bad guy" while calling two criminals who shot someone in the back and then kicked the shit out of him, nothing at all, leaving them to be "the good guys."
This is an important point that the police apologists will not respond to. Derec in particular loves to bring up the past misdeeds of black victims of police violence (or vigilante violence as in the Trayvon Martin case), but will not focus on the fact the police (or vigilante) committing the unjustified homicide is doing something far more heinous than anything the victim may have done. They are killing people.
The postmortem smearing of the victim's character serves several purposes:
1. It is an attempt to dehumanize the victim, and portray the killing as an act of putting down a rabid animal,
2. to portray the killing as an act that is beneficial to the public interest (in fact, one poster in this thread actually commented that Mr Brooks' family was better off with him dead),
3, and to draw our attention away from the fact that the killing was unjustified.
The apologists will tell you that the police are allowed to shoot a person in the back, stamp on his body and kick it because that's just a normal human reaction - nothing wrong with that at all. But that shoplifting or possession charge from 10 years ago? But that this black man may have been terrified of the police which led him to act the way he did? Inexcusable! The world is a better place without such scum.
The unstated assumption behind this strategy is that the lives of black people killed unjustly by police are not worth protecting, and not worth getting worked up over when such incidents do happen.