Maybe don't open spam emails/private messages then? Oh, and welcome to the internet.
Wait... So, there's a Mercury reader that doesn't smoke weed? Wow.
I refuse to believe that there's a "freak" in Portland. That sounds pretty unlikely.
While posting on this particular blog might have the desired effect, I recommend using your dating website's "Block" feature, usually these things also have means for reporting verbally abusive users as well. Regrettably, a lot of people think this behavior is perfectly acceptable and use lame excuses like "welcome to the internet" or "this is the internet" to justify such actions. For an example of this read the first comment. Some people hate hearing no and want 420weedsex so bad it sends them into a trolling rage, sorry anonymous.
Call me crazy, but I don't think saying "Better luck elsewhere, but I'm not 420 friendly" is an effective method of ignoring someone, and it certainly doesn't fall under the "not writing someone back" category, Anon; NOT replying to someone actually means you DON'T send them a message back.

Get over yourself!