@Ramhound, interesting story. Anyway, I'd say two things. 1) Don't descend to the level of those that do that. 2) People not being invariably dedicated to fair play, perhaps your story indicates a need for a kind of spider software that checks for possible revenge vote system gaming/bullying -- the practice would leave a distinctive electronic footprint. i.e. there'd be an initial downvote, followed by a cascade of them. Using SE's internal (secret) database would be ideal, but detecting likely correlation via the public database would be the more challenging programming problem.

@Ramhound, if it's any consolation, this practice of revenge voting is not universal. I've sometimes scanned profiles of disagreeable commentators, (to "consider the source"), and most often find reasons to upvote their other (better) posts, or ignore them. In light of which, a policy of preemptive closing seems like a weaker iterated prisoner's dilemma strategy.