We always play together on duo/3 man groups max, i can voucher we never afk in BG's unless there is a valid reason (something coming up IRL, or just a quick toilet break).
The only BG we did afk was on silvershard mines where our team stopped getting out of the spawn because we got decimated by an alliance premade.
If he got banned for that, then a lot more people, including me should have been banned accordingly since no one was going out of our spawn.
However the case, I don't feel it's a valid enough reason to ban someone for a single BG spent afk.
Edit: after discussing we uninstalled MOP, my post was intended both as criticism and as a warning for people coming to the server.
Kindest regards,
goodbye