re:Ikarim

Question

Some of the Baalei Tosafos and other French and Ashkenazic Rabbis believed G-d was physical, and this was the basis for the major dispute between them and the Rambam. A professor named Marc Shapiro who often posts things on this site recently wrote a book that touches upon this controversy and concluded that the so-called fundamentals of the Rambam are "optional" - a matter of personal choice, not required beliefs - because we see that many gedolim disagreed with them, so they can't really be "ikarim". I personally think he fails to prove his case convincingly, since even in the times of Tanach there were "great people" who in fact believed false ideas, such as Micha or Achitophel. It seems perfectly possible that people living in the times of the Rambam, regardless of their titles, may have been heretics. The Ramban (Nachmanides), when discussing this issue, actually states in one of his letters that anyone who believes in such nonsense - that G-d is physical - will burn in Gehinnom. Mr. Shapiro conveniently omits that phrase from his citation of Ramban in the books, attempting to portray him as a bit more "sympathetic" to the heretics. In any case, this professor thinks that to be a good Jew you simply need to follow the laws, and it doesn't matter whether you believe Hashem is incorporeal or has a human form. How would you respond to these claims?