Some people get their highs off of destroying other people. It sucks, but I wouldn't let it get to you. Or at least be down for a bit and then cheer up to know that you're better than them because you didn't retaliate and you don't do that sort of stuff to other peope, particularly aspiring RP creators.
Delete the post from the cbox, dismiss the person as being an idiot and look forward to a prosperous RP! xD
Hey, I say everyone deserves their own opinion, but one doesn't need to go overboard with it. >_<
Don't let the inconsiderate guests get you down. Make your site - they'll be missing out on a great time.