Because it works. Reagan routinely called liberals out on their BS and was hugely successful in getting his agenda passed by an often hostile Congress. Reagan would routinely use mockery as a weapon to great success.
Contrast this to the past 7 years of George W. Bush telling everyone how he loves to work with certain Democrats, and look where that got us.
This is an election, not a essay writing contest, if dirty tricks result in conservatives making some kind of political comeback in 2008, then so be it. Preserving this great country, at least for me, is more important than playing "fair."
You see no difference between 3rd grade tactics and embracing your enemy?
Stick to the facts and the issues!
There are key distinctions to be made and if you stay focused on those differences it is more diffuclt for the opposition to dismiss you.