Except for the tiny detail that Sherlock is himself a man, written by men, so any advantage he gets over male characters is simply a redistribution of the pies between Team Men on the say-so of men. Open to criticism, sure*, but none of it gender-based. Favouring Sherlock over female charcter, otoh, means passing advantage between male and female characters; obviously, this can be sexism.**

* _{F'rinstance: the "you lower the IQ of the whole street" comment may well be beloved snark of some fans, but plenty of people find it the sort of overt obnoxiousness that puts them off Sherlock, Anderson's S3 breakdown is hardly popular, and Moriarty remains pretty divisive. "The showrunners are too in love with the main character" is actually a pretty common criticism of Sherlock.}

** _{Obviously there is still room for debate. I have zero fucks to give about Sherlock shooting Milverton because he desperately wanted murdering and Sherlock was most likely to get away with it. But "what about the menz!" is not and never will be a decent rebuttal to accusations of sexism.}