agreed NPC bounty is annoying, but from the OP's post he was constantly killing friends, hookers and sticky bombing using tanks ect... R* could see that as trolling, i do think a 2 day ban is abit OTT i think a warning system via a text saying something "warning killing team-mates/players continously could be seen as griefing and a 24hr Ban will be applied". I think R* use a ticket rate on free roam for example if you continously kill the same player "joe blogs" that the ban comes in play but R* wont tell you that.
Im not saying that the whole point is not kill players, but killing the same player over and over past the ticket rate can be seen as bad sport, cause your'e not giving the other player a chance. but dont take my word as gospel.