Not a whine, read before you rant.
There's no benefits to killing in Freemode, even for trolls. There's usually only negative effects to the player who was killed, and actually, negative effects to the killer.
Max xp you gain per kill: 100 (I don't even know the minimum because I haven't killed in Freemode, see no reason to)
Sure, maybe this is how you rob a person, I don't see you getting 10k, and even if you use this tactic to farm for cash, your skills stay ultimately sh*tty.
Chance to waste extra ammo
Chance to damage or total person vehicle
Pay Hospital bill
There's no scoreboard so you can gloat, either. So I seriously don't see the point in it. It seems entirely more logical to go back to GTA4 and kill people in Freeroam than here. And no, I've actually never been killed in free roam, shot, yes, but I've never paid any Hospital Bills.