I have to be honest with you, the fact that you found a psycho in the Sonic The Hedgehog community doesn't surprise me at all. Some of the most obsessed, immature anime fans I've met, hide crazy under their plushie collection!
The truth is, any community online has the potential to have these people. We all take that risk when we post, and especially when we do an action figure trade. I've been lucky that so far the people I've dealt with have been nice.
I wouldn't worry too much about it. This guy sounds like a really sad individual. E-mail spam lists and mean messages online is without a doubt the worst he can do to you. He doesn't have the power, resources or finances to do anything more. Just ignore it.
Also, the fact that this person is a member of another online community you are no longer a part of, could be a sign that maybe you need to just step away from the Internet. When anything that happens online directly affects you in real life, chances are you've let it go too far.
The Internet is a fun distraction, but it matters not in life.