To quote (or perhaps paraphrase) R’ Ahron Feldman: “One argues with Chazal is not a heretic, just an arrogant fool.” I think the ame can be said about most people today arguing with the Rishonim and Achronim.
I argue that when calculating the disgonal of a triangle, you use the Pythagorean Theorem of “A^2 + B^2 = C^2” (for a right triangle).
Rashi and Tosfos disagree (Bava Basra 102a, Dibur Hamaschil U’Kigon).
Am I an “arrogant fool” for doing so (instead of other reasons)?