For all that are un-happy with this change , I would like to refer to a post I made a while ago ( with some extra stuff that can be trimmed away to save on dev time )
Link: https://octowow.st/forum/viewtopic.php?p=1421#p1421
I don't believe players should be punished for pvp , but incentivized. I believe the goal is to incentivize players to kill gankers rather than punish the ganker.
Tl;dr: Offer some reward for turning in the "head" of someone who's flagged for killing Grey level players. Idk what the reward could be so the devs would have to figure that part out. But all I can is can you imagine the kind of heat you'd bring on yourself if people knew they could turn in your head for a chance at a mount ?