Whether it was on a newsgroup, or IRC, or anything, from the beginning of time (well, the internet), the mantra is
"Don't Feed the Trolls."
And that's what he is. A troll.
Leave the comments up on your marijuana toxicity post, since they're not as abusive, and it leaves it open for different points of view, but if I were you, I'd
remove them from your about page. That wasn't necessary of him. In fact, I'd close commenting on that page if I were you.
Just my opinion, of course.