I will tell you why people are getting upset. And it has nothing to do with "PvP" or Bioware. Decent people are upset because they see great injustice. Because they see pathologically anti-social emotionally crippled people destroy innocents.
You will see people with common decency and tact queue up and wait for their turn filling up 4 men group to make it go nice and orderly. Than a group of sociopaths from Clockwork orange will roll in in their bowling hats and impenetrable slang and destroy, maim and sadistically mutilate, while singing "trolol" in the rain.
"But Bioware flagged that quest as PvP!" is not excuse. Just because something is not against the rules, doesn't make it right. It wasn't against the rules to throw people out from "whites only" carriages. I am sure there was bunch of apologists back than too.
If the quest actually said "Kill X players carrying bubbles" or something along these lines, than fine. But it doesn't. So when you choose to attack someone merely because they happened to be there, doing their own thing, it is you being anti-social creep. My only hope you grow out of that phase, but my great fear you are the type of person who would always just ever look for "Number 1" Type of person who would hog all the food on disabled cruis ship fot themselves, with no consideration ever for your fellow men. Well, they aren't really your fellow men either, are they? They are merely undermenchen, "carebears" to be tortured and destroyed without much of a care, isn't it right?