r_beau -
It's always a clue, when the site doesn't have a privacy policy, that what you post or email may not be real private. You can file that information away for the future.
But your letter to them was a decent one and you got to say what you wanted to say. Probably a lot of people who visited the site agreed with you, too.
In order to bring a defamation suit, though, the language has to be pretty rough - debates often get heated and words thrown back and forth can get nasty, but that isn't defamation, usually - it's free speech. Plus, with a defamation suit you'd have to show damages - real proof that your reputation was harmed. None of us saw that.
And, finally, it is expensive to sue, and time consuming. It is best just to chalk all of this up to a lesson learned.
By the way, I love North Dakota. Very cool state. And good luck in med school!