The fallacy fallacy is when you say something like "Argument A for conclusion c is fallacious, therefore c is false". I know seen the misuse of the ad hominem fallacy referred to as the "ad hominem fallacy fallacy", but I've never seen the misuse of the straw-man fallacy be referred to as the "straw-man fallacy fallacy".

It seems to me that he is saying you are straw-manning for not making your comment specifically tailored to his opinion but rather basing it on the common view regarding child-adult sexual behaviors. But then follows up calling your comment a straw-man by saying that its not one, but rather it is just the response to a different opinion than his own.