It can be a derogatory term with a sexual meaning, but it also can be an offensive term for those involved in the American "tea-party" movement. I would need to see more of the reading to determine.

While "teabagging" does refer to a sexual act (which I'll hold off from describing), you are more likely to see it as a term for a person involved in the Tea Party movement in the US. At this stage in the Tea Party movement, "teabaggers" is a pejorative term. People against the Tea Party movement refer to participants as teabaggers. Those within the movement are more apt to call themselves tea partiers.

This is a very very dirogitory term and should not be used.

If you ever want to know the meaning of slang or derogatory comments, use the online urban dictionary.

It means someone who drinks tea. It is OK to call friends who drink tea drinkers teabaggers. 人們誰喝茶. 是好叫朋友們 "teabaggers".