I think the point here is not so much that there was a group on board but how it was handled. I think most of the cruises that we've been on, there has been some sort of group on board. Several times, it was some sort of car dealer group. Naturally, the group tends to interact amongst themselves.
But the problem here, was that there was a very large (1/2 ship) group on and the "ship" catered to their "needs" while not making appropriate accomodations for the other passengers. Shuttling off "other" passengers to La Verandah for a buffet dinner is totally inappropriate. Besides, this goes totally against their policy of "open seating" at dinner - at least in the main dining room.
As was telling people waiting for the tender back to the ship that they weren't taking anyone back because they had to get the group off the ship.