Originally Posted by stickypaws
Sarcasm tends to elude you, yes?
The meaning of rhetorical devices tends to elude you, yes?
You're not mocking him. You're simply pointing out the hypocrisy in his complaint. It's not sarcasm.
To help figure out whether something is sarcastic, say it out loud, and if you didn't use a sarcastic tone of voice, it probably isn't sarcastic.
If you had added something like: "What a fine grammarian you are!", then it would be sarcastic.
Note: I probably screwed up the the grammar somewhere in that last sentence. A quote with an exclamation point mid-sentence is not something I usually deal with. I think the comma goes outside because of the exclamation point, and I think you need a colon before a quote that's a complete sentence, but I'm not sure.