In a lot of political blog posts, you'll find references to the "Overton Window
". This refers to the range of opinions on a subject which are considered acceptable in the current political discourse. People often talk of "moving the Overton Window" so that a formerly unacceptable idea can become mainstream. For example, this Kos diary by One Pissed Off Liberal
claims "We’re moving that Overton window! All of our screaming and bitching has changed the national discourse!" on the issue of impeaching Bush and Cheney. It used to be that talk of impeachment was considered "beyond the pale", but now more and more liberal activists are seriously considering it. (Not only have I considered it, I think it would be a very good idea.)
One common technique for getting an idea into the Overton Window is to get a more extreme version of the idea out there. Then the original idea looks more reasonable. So all those wingnuts spouting extremist nonsense are furthering the right-wing agenda: rather than making the right look stupid, their hateful, eliminationist rhetoric ("God hates fags and wants them to die!") serves to make policies that are merely bigoted ("Gay relationships shouldn't have any legal protections") sound "reasonable", "serious", and "centrist" in comparison.