Because they are named "teabaggers" by your group. They are doing the teabagging, your side is who they are teabagging, hence you are the teabaggees.
You should be proud to announce to the world how you love being teabaggees, so that people can continue to "giggle" when you try to dismiss their protest by calling them "teabaggers". Open wide.
1. Not my group.
2. Looks to me like they are trying to do "teabagging" but failing miserably and thus getting "tebagged.