It is also insulting to FtM aspies, and cisgender female aspies. A FtM aspie could be dismissed as not "really" being trans the way NT people are trans. Female aspies meanwhile get their gender identity diminished by being told they aren't as feminine as NT women. In fact I saw a study earlier in the year that tried to use the male brain theory to attack FtMs, as being "more autistic" than other populations, and therefore (according to the study's ableist language) mentally deficient.
"Overly male" in this case would refer to a theory that the male brain is characterized by a systemizing, analytical bent, and that autism represents a brain overly devoted to analysis and systemizing. There is no proof that either claim is correct. There's still a lot of research going on concerning differences in NT versus autistic brains, in order to produce a cure, but nobody has one yet, clearly. On the other hand, while the brains of men and women do differ in structure slightly, debate continues over what that means in practical terms.