Popa,
It is not bizui of the talmud chacham to opine that he was mistaken, if the tone is respectful. If he would have written “the Rambam was a bigot” then I would be maskim. If someone says that the Rambam was influenced by the mores of his time and those mores were sexist, that is not bizui.
For example: Aliyos for women. I don’t think there is any issur if a person says that the pashut pshat “kavod hatzibbur” referred to in the Gemara is based on the sexist mores at the time, and today that we are not as sexist there is no problem of kavod hatzibbur.
That isn’t even saying that today’s mores are superior to the mores in Talmudic times, it is just noting the factual difference in mores.