Larry,
Not to step on Republic's answer, but I believe that you had a similar experience that I did. The PM was polite and I was on my way to work in a matter of minutes so I replied, and told them to enjoy their practice and to come back.
My first initial feeling was, "Who gave them the right?" But since, we had been talking on country vox previously and he had explained what they were doing, I found that his request was merely to leave the area in which they were engaging. In this case the AvA was no different from any other night, if I had chosen to stay and look for fights from any of the other numerous bases.
You and I had a brief encounter (which I loss rather quickly) and if my schedule had been any different, it would have been my pleasure to oblige you with some target practice.
I think that you and I, and the majority of the regulars to the AvA, enjoy the kind of adventure provided by multiple contacts. So, seeing the numbers above 20 in the arena, and logging in and being asked not to participate was quite a tease.
But one thing that the squad's activity did, was draw more attention to the arena as an alternative to the others and consequently brought more players in than an arena showing 0- 3 players logged in.