So, I have installed WordPress 3.3.1 +Buddypress 1.5.2. + Buddypress Default Theme.
I Created few members and created a group and made the members join the group.All the members are friends with each other.
After joining the group when a member Goes to Invite page and then select the members from the list(Although the names appear in the list are already members of the group) and then unselect them and refresh the page, the members disappears. I put up a video to make it clear:
Note:So, from group invite page, just select all the members and then unselect them and then just refresh the page and the members will all be kicked out of the group; even the admins and the mods.