No matter how horrid it was, it's just words on a screen. How could it have been so bad that you were forced to shut down your account? Who did they tell these things about you to? An employer? A family member? Why is it such a threat to your reputation? Furthermore deleting your account doesn't delete THEIR comments. No need to shut out all of your other fb friends.
Never argue with strangers on public posts. Otherwise, fb is nice.