No, it sounds quite serious to me actually. I don't joke around like that even with my friends.

we're not disagreeing here - I'm saying he's being sarcastic and rude. the tone of that message is patronising and it's just an unnecessary jab.

Assuming you're not a jerk and you don't say jerk things, you wouldn't have said this jerk thing being quoted. So saying you wouldn't have said it doesn't change the meaning of what was said.