IANAL, but it sounds like his case would be very weak. You clearly had the domain name before he filed for the trademark, you have not been actively trying to e

IANAL, but it sounds like his case would be very weak. You clearly had the domain name before he filed for the trademark, you have not been actively trying to extort money from the trademark owner (you've not responded to his requests to buy it), and you're not trying to export customer confusion to his name. If you really care about this, hire a lawyer. If you care a little bit, but not enough to pay someone, then it would make sense to put something on the site to make it clear that you're using the domain name for something productive that is non-competitive with the trademark registration. As you correctly point out, trademarks are for business domains (or geographic domains, but that seems really quaint these days, right?) so a legit use outside his trademark domain would mean his complaint was null and void.