i wouldnt necessarily call them conservative, if I'm not mistaken they are both quoted as saying they try to toe the line with their comedy...and they do a very good job at it.

take the episode "best friends forever" for example, which was a take on the terry schiavo fiasco.

when kenny's will is finally discovered, and the part of being in a vegetative state is read, they have the option of going the conservative route (pull the plug) or the liberal route (let him live), yet instead, the part of the will reads "if i am ever to be in a vegetative state please, for the love of god, don't ever show me like that on national television." ...classic.

contrast this with family guy, who in recent seasons has really taken on the ultra-liberal persona of its creator...this leads to alienating a lot of people, and frankly, being not that funny.