Of course the cops are "people", logically, but GTA itself treats them as disposable units.
They make them corrupt assholes to a (hopefully) unrealistic degree.
"Man, I sure do love to beat civilians."
"KILLING PEOPLE MAKES MY DICK HARD!"
"I GOT A SHOT AIMED RIGHT AT YOUR BALLS, f*ckER!"
"The dipsh*t- I mean, 'suspect' has a weapon!"
(There are certain lines like "tell my wife I love her, okay?" which seem to totally contradict the other ones, oddly enough. I don't have an explanation for those, but the ends justify those means.)
And that's just what I remember from Liberty, the fat, slow cops. The roid-rage west coasters are the real murdering maniacs.
GTA is a game were fighting the law is a crucial part. They have to give you honest reason to show little remorse when killing them.
In games less focused on killing the law, they try to make them more realistic and "human", Manhunt, Red Dead Redemption, and sh*t, L.A. Noire.
In a story, you're forced into a perspective. You're supposed to either sympathize with, or at least, understand the criminals', the "bad guys'" motives.
I just replayed a game called "Destroy All Humans!" (PS2 classic, play it!) You're an alien. You go around murdering a bunch of humans; especially cops. But you are encouraged to do so. That's the game and the perspective you were forced to sympathize with. It was fun ride exploding men's heads all over the 1950's landscape and them having the media blame it on Communism.
I don't care that Trevor killed cops, or that Michael, or Franklin, or Niko, or Tommy- whatever.
I don't care that Trevor killed the O'Niels or the Aztecas. They were hostile toward him. Maybe the O'Niels have a backstory, but from what we know, they're victimizing Trevor, so T is the good guy.
But Johnny and the Lost have a deep backstory, one that took up a whole f*cking game. And Floyd's backstory is not explored, but presented. He's a softie who works a hard, blue-collar job with an abusive girlfriend. Why don't we like Trevor for killing them? Johnny, Terry, Clay, the Lost, they all have their own sophisticated backstories and motives, and the circumstances under which they're killed are too unbelievable.
Trevor shoots Johnny in a wild-west style duel showdown? Fine. Johnny inexplicably becomes a druggie, moves out west, with his dumbass girlfriend he ditched in IV, and he gets just creamed? f*ck that. Terry and Clay run with their tails between their legs just to be killed by a little bumper tap? f*ck that. Floyd is an innocent man who has his life swiftly destroyed and gets murdered as some sort of justice consolation? f*ck that.
They portray what Trevor does as unjust and villainous (by showing Ashley crying over Johnny's body or having him attack the Lost when they're openly mourning their dead), and they still expect the viewer to sympathize with him.
Out of all the Lost bullsh*t, I really think the hardest to justify is that funeral mission. "lol lets kill everywun kuz extra mission in this sh*t, watered down game"
The Lost are already in travesty and disarray. Their leaders are dead, their business is destroyed, and when they try to mourn, Trevor just kills all of them for like the f*cking sake of killing sh*t. (Like that doesn't happen anywhere else in this game.)