I think that the fulcrum of the argument over 'Game Facilitation' you guys are having is whether the job of policing such 'disruptions' is a default for facilitating the game, or a special part of that facilitation in some games where the table as a whole has agreed to that.
In other words, should players seeking a GM veto on actions where one PC harms another bear the burden of seeking the agreement of their fellow players? or should players seeking an 'anything goes' experience where other PCs don't get to veto their actions using the GM or social contract bear the burden of seeking the agreement of their fellow players?
This is chiefly a cultural, and ideological difference, is PVP something the group has to opt into by specifically deciding its ok, or something they have to opt out of by agreeing it isn't. Everyone has a perception of a default (or lack of a default) social contract, to some that contract might stop shorting of protecting the characters from one another, to someone else, they feel that they should have a right to restrict another's player characters actions should it harm their character. Establishing an agreement about it at the table is obviously a useful way to present this, but who has the emotional right of way barring such an agreement?
There's an interrelated but separate question of whether such proscriptions are valid in cases of incidental harm e.g. 'dude I'm throwing this fireball to hit all the enemies, its not my fault you decided to run in the center after I mentioned it! I don't care that you're standing there.'
The overarching point I think you're making is that it's really a table by table "agreement" whether that agreement is literal or simply plays out organically through the soft dynamics of the group at play.
Ultimately, I suppose this isn't really a matter of right and wrong (like with most things), but I am definitely
strongly biased towards the notion that people are simply there to have fun - it isn't a job, either for the GM or for any of the players. If the group is having fun, they will continue to play, if they don't, they won't.
But it's simply my opinion that it works a lot better to distribute GM responsibilities and therefore ownership of the game. The GM should
not be given either all of the "work" or substantial power by default over all other players when it comes to general table etiquette and dynamics. This can lead to toxic psychologies for all parties and
increases the likelihood of conflict. I think it's a problem that the core rules still peddle this idea as I see it as very, very outdated.
For example, in my current campaigns one of the players manages all NPCs in combat. Another player handles the cartography. Another player keeps track of stories & party inventory. This all works because everyone that's playing is a competent adult and it's a shared, cooperative experience so there's a built-in social contract. The only real difference between me and the other players is that I provide more narration as the person who has the best beat of the setting and the adventure. Even with regard to rules arbitration I'm only
slightly above other players and it's only because I happen to know the rules the best in my group so they tend to defer to me. But it's not hard to imagine a situation where a player has more rules mastery than I do and me handing off much of that responsibility to them.
I mean, frankly, I literally have never dealt with a situation like the one you're describing.