I'm pretty sure half the guys on dating sites send the "whats up, how r u" type messages to women who specifically warn against it just to piss people off. It's humorous to many to be able to get a strong reaction from someone for such little effort.
I have to say, though, that you seem to be making as many if not more assumptions about this guy as you're postulating that he is making about you. It seems harsh. Telling someone in the first message that you aren't really looking for new relationships seems very much like telling someone in the first message that you are not interested in looking for dates, let alone a date with him.