Sam2 and Yitay,
The example I gave would be apikorsus even according to the Rambam. It is in the category of Pirush that is Halacha L’Moshe MiSinai, like pri etz hadar being an Esrog.
In other words, Chazal are saying that “eye for an eye” always meant money, it was never meant, or practiced, literally. To say Chazal were lying, and they didn’t really get it from Moshe mipi HaGevurah but instead made it up, is to deny the Torah Sh’bal Peh as being min hashamayim.