If I searched and remember right, the last debate with Truthers I participated in was the comments of this diary from June 2007 (almost precisely two years after ET's founding). I don't remember anymore exactly when that line was added to the guidelines and with what consequence it was enforced regarding Truther diaries, but there was no talk of banning in that particular diary. At any rate, the dustup involving aircraft engines Migeru must be referring to is this (continued here and here), nine moths earlier, apparently prior to the creation of any guideline.

_{*Lunatic*, n.
One whose delusions are out of fashion.}