If this guy's track record is to make bad and ineffectual copies of up-and-coming business models, then neither you nor others would benefit/have benefited from

If this guy's track record is to make bad and ineffectual copies of up-and-coming business models, then neither you nor others would benefit/have benefited from being warned beforehand. Imitation is the sincerest form of flattery, and investors like businesses that have competitors (it validates the space). This clown has just paid you two kudos, gratis. The best revenge is to watch him fail (by succeeding, yourself). Holding a grudge is like letting someone live in your head rent-free.