I am far from being sarcastic. It is derogatory. That is the purpose of an insult. That is how Rush uses it.
I have never taken it as such - mainly a cute phrase to highlight children during the learning process. Like I said, some will find anything to be objectionable. Such is the world of political correctness and hyper-sensitive types. Reviewing your posting behavior (in my opinion) has a history of that. Good day.