It's pervasive, because society rewards it, by and large. From Perez Hilton, to the unprivate woes of the Jon and Kate Plus 8 couple, it seems like we all love to hate.
I know for a fact that I'm as guilty as anyone of behaving badly, and maybe more guilty than most. Like the food critic in Ratatouille said, it's often fun to be negative and mean for it's own sake.
Don't forget that a little cynicism is healthy. Certainly, it doesn't hurt to be unafraid to point out to someone that they're pissing on your leg and trying to tell you it's raining.
But how much is enough? If you're a bottomless pit of cynicism, how are you going to enjoy life at all? Who even wants to spend time with you if everything out of your mouth is a critique?
Like all guilty pleasures, negativity is something that you have to enjoy in moderation. If, like booze, you feel powerless over it, maybe the best thing you can do for yourself is abstain.
Another alternative, is that if you indulge in negative commentary, follow it with something positive. Say to yourself, "Now say something positive." Much like a palette-cleanser between courses, refocusing on positivity will help get the taste out of your mouth.