As DeepEyes has said, when we were boosting and someone dropped we would get 1 japanese player that would constantly join. Given the game is barely played by anyone I very politely asked them to leave, I explained that were just trying to get trophies done and that's it. That person went on somewhat of a rant and tried telling us how lobbies work and that we will never be able to boost in a controlled group (even though we were already doing that for 10-20 hours at that point), when I tried to re-explain myself that person kept repeating his point and refused to listen.
Granted, they are in no way required to listen to me and do as I ask, so I accepted it. We left the match and tried re-joining each other, but from that point forward every time we wanted to connect and have a full 6 person boosting lobby, we would always run into them, they again kept refusing to leave the pre-game lobby. All of this just lead to us seaching for each other for an hour, while that person sat in a lobby and watched us go in and out of it and I can tell for a fact that was neither enjoyable for them or us, just waste of time.
But hey, that's boosting for you, you can't always expect people to comply. They were just trying to play the game normally, while we were trying to get our trophies done. I am not sure this thread will do you any good, people are people, you sometimes get rude boosters who tell you 10 different ways to fornicate with your dead relatives because you dared to join them and then you have players who post videos on youtube where they disrupt boosting sessions, because boosters are "noobs" (I mean duh', there's a reason we don't try to get trophies the natural way) and deserve to be purged.