It's not harassing, at least I don't think so, but it would help to know what you said.
Nick, mind just copying to us what you said?
Honestly though, it's probably nothing that horrible, the principal probably won't care, if you just used one word. That's hardly harassing, and there are so many worse things going on. Friends of mine bitch each other out all the time on facebook using forget this, forget you, blah blah blah...haters gonna hate.
But still wanna see what you said :|