Okay, in all honesty, I would have written the above e-mail but then only sent this part:

Thank you for bringing my son's response to your assignment to my attention. I am assuming you are taking issue with his use of the words "hate" and "sucks" as well as the negative tone of his response. I will discuss these issues with him.

I think just having been that kid, I am defensive.

Another trick I did when I was his age was I picked out a kid I knew the teacher liked more than me and wrote it how I thought that person would respond. There was still a fair bit of sarcasm but once again it was not something for which I could really be penalized.