This letter is an apology for name-calling during an argument that got a little out of hand.
Some things are said in the heat of anger, and then regretted later. So please realize that I didn't mean it <time of argument> when I said <hurtful thing you said>. I know you were hurt, and I wouldn't blame you if you didn't want to talk to me for a while. But I have a suggestion: when you do decide you want to talk, I'll give you a list of rotten names you can call me, and you can go at it to your heart's content. Everything from <rotten name> to <another rotten name>. Please forgive me, and I promise it will never happen again. I hope we can talk soon.