The two, and adding Wilson/Brown, are different instances. Each resulted in dead "perps". While Zimmerman and Wilson are, in my opinion, good shoots, this one is not.
You can try the case in this court of public opinion, just as others will. Your attitude is that those find fault with Slager are somehow not fair is simply your opinion. Wrong, in my opinion.. Boil it down to the bare facts and Slager was NOT in imminent danger, the perp had disengaged and was fleeing. No one, certainly not a civilian, has a justification to shoot an unarmed person in the back. Not unless it is a war zone and a soldier is simply liquidating a combatant. Now, if you wish to state that cops are working in a war zone and the citizenry are the enemy....well then, we have an issue that too many cops today seem to perceive it to be.
Serious question — have you assessed what is posted at the link? And no, I never said those who find fault with Slager are unfair. I definitely say those who condemn him without doing due diligence are unfair. What’s fair is to assess all factors and apply the law.