Same thing happened here OP,
we were having a giant convo in trade about celebs back during BC and I said something like 'I'd nail Brittany Spears" and I got a 3 day ban. Mine too was listed under harassment of another player and I sent blizz an email asking who I harassed because that wasn't harassment of any other player they said they couldn't divulge that information. SO apparently Brittany Spears plays alliance on the scryers. I didn't know so many celebs played WoW!!! XD
Anyway, perm ban? Hell no, I've seen kids saying, no SPAMMING trade with 'Fa**ot n**gers!' and they never get banned. Most you'll get is a 3 day ban.
But its funny, because after I got banned I too have kept myself out of trade chat in ANY game. I used to be the dude with the witty, oft profanity laden remarks in trade chat, and I was somewhat 'known' on my server for not putting up with anyone's shit so if I saw someone getting bullied I'd usually totally embarrass the bully in trade chat.
Anyway, no perma ban (though you might have the NSA show up at your house depending on what you said) you'll be okay... until the NSA shows up :P