Those people get their jollies when you respond. You are correct about not answering him.
Out of curiosity I was doing a search online to see whether I could tie the email address to an individual (have his name already, of course). Interestingly, one search engine provided a link where that same email address was used. It took me to a site where an individual who identified himself as a FReeper had a blog or other some-such site. The guy who emailed me left a reply on that site which was also pretty obnoxious. The same email address showed up as part of his name/contact information.
It's obvious, to me at least, the guy is a stalker. Maybe someone with more Internet savvy than I can find out more about him. As for me, I've saved the email for posterity, and have set him up as SPAM on my email server. I shouldn't have any more problem from him.