I posed this question on GovLoop's Facebook yesterday and got the following responses:
Steve Boggio I find that they have to go negative because they don't have facts on their side. I positively rebut using CBO,BLS, CBpp, etc sources. I also push back with the alternative buzz words that characterize the alternative that they fail to mention.. Iike ObamaCare - BushyCare, trickle down - trickle ON
John Bordeaux I have exited comment threads when someone goes beyond negative. Most recent example, someone who said: "I heard a rumor that 60% of the military hates Obama, so a coup is likely. I hope it's peaceful," At that point, I advised the commenter to seek professional help and "unfollowed" the thread. There has to be a limit, no?