I saw an interesting counter-example recently. Someone who really should have known better tweeted an extremely offensive and defamatory comment about someone else, including their twitter handle in the tweet to make sure it was seen.
It struck me as particularly odd, as a similar (incorrect) conclusion could have been reached, from an analogous situation, about the originator of the defamatory tweet.
But what impressed me was how the subject of the tweet responded: and that was simply by ignoring it.
No rebuttal, no counter-accusation, no ad hom... nothing.
It would have been easy to refute, easy to threaten an action for defamation come to that, and certainly easy to accuse the accuser of double standards and worse.
And as a result, there has been no brouhaha, no fuss, no gathering of gangs and mutual recriminations.
I don't know what the originator of the defamatory tweet makes of it all; whether it is perceived as having been unanswerable or (with hindsight) stupid (or worse); but the wonderful thing is that the recipient doesn't seem to care.