Rambam - how could he learn from heretics?

 Chida (Pesach Einayim 1:202b): R’ Meir found a verse and interpreted it. The gemora did not simply say, “R’ Meir found a verse.” This implies that only R’ Meir interpreted the verse as permission to learn from a heretic while the rest of the sages disagreed with him. Thus according to the majority position there is no distinction between an adult and child learning from a heretic. That is why the Rambam omitted such a distinction in the Mishneh Torah. This is also the understanding of the Shach (Yoreh Deah 246).  Others disagree with this interpretation  However if the Rambam rejected R’ Meir’s position that a mature adult can learn from a heretic - how could he himself have learned secular knowledge. He writes in one letter that he learned all the books of idol worship… Furthermore we find that the Rivash (#45) said that the Rambam learned philosophy because he accepted the view of R’ Meir that a mature adult is allowed. The Rivash also notes that the Rambam cites the verse of R’ Meir in the introduction to Moreh Nevuchim! I think the resolution of these difficulties is what I wrote elsewhere. The Rambam’s definition of mature adult is not great in years but rather great in Torah and with an advanced mind even in matters of the world as was R’ Meir. Therefore, if the Rambam wrote in the Mishneh Torah that a G-dol was permitted to learn from a heretic, everyone would view themselves as a Godol and permit themselves to learn from a heretic. Therefore, he deleted this distinction. The spirit of G d spoke in him, in particular in our orphaned generation where every student thinks he is a rabbi. They are in fact naked and yet they are not embarrassed…