When you take terms with vile connotations, like rape, murder, child abuse, and racism, and expand them beyond their conventional definition, people use scare quotes around them because they want to make it perfectly clear that they are unwilling to give your use of the term the really, really bad connotations that their use of the term carries. I'm willing to bet that's basically what's happening here: what you call "child abuse" is not actually bad enough in his mind to merit being called "child abuse."