Maybe there is no other way than an invite only group or request for an invite group to be able to moderate it properly for the owner.
It is annoying we can't woop people from an open enrollment group permanently as SL avoids such

And I have seen what you are talking about as well, Kendrah.
It is hard to fully understand people sometimes no matter how hard we try.
Now I think of it it is possible to have an open enrollment group with in default no rights to chat and post notices.
Those right can be managed via request and in an other role within the group.
It is too stupid for words this is needed but that way there can be a naughty corner