You did the right thing and yes, I think it's best to not reply to that sort of crap- it puts you down on their level. I think I've mentioned on here before what I had to do when I got a very vicious, threatening PM back on obt. I know it's easier said than done but usually in that kind of case it's best to totally ignore it because by replying you feed their "fire". It's kinda like continuing to give in to or reason with a 7 yr. old who's throwing a tantrum. I've learn the best thing for me is to try to bite my tongue and ignore nonsense.