I don't think you know how to use the phrase, "calm down". It is typically applied in situations in which a person is overly excited for medical, emotional, mental, traumatic, or otherwise provocative reasons. Examples include, winning the lottery, uncontrolled anger or exasperation, panic at terrible news such as the death of a loved one etc... It's never too late to learn how to use speech appropriately and in context.
My comment was not "knee jerk". I actually thought on it about a half-hour before deciding to go ahead with it. Because yes, there may be people who believe as you say the OP is not one of them and gave no indication of such. The meme you posted along with the comment say exactly what has been interpreted. You were applying it to him directly. You even went so far as to take a sarcastic photo of yourself to use in the comment. So looks like the one who is having problems here is you. And that's okay. You will get better with your communication skills the more you use them..