The tradition of a Gezeira Shava

Question

A number of questions and answers (here is one, for example) have pointed out that expounding text by means of a gezeriah shava requires a mesorah, a teaching from one's teacher, and that different talmudic sages accepted or didn't accept a particular gezeirah shava because they had no tradition to learn it as among a particular list of accepted examples.

But if all the sages can trace their learning back to an authoritative source, wouldn't rejecting another sage's G"Sh be tantamount to accusing him or his teachers of lying? My teacher might not have learned it from his teacher, but your teacher must have gotten it from somewhere, so unless I claim that somewhere in the history of your teacher, someone made one up and your entire tradition is a lie, I have to concede that your tradition is valid, so how can I dismiss it?

Answer 1

Rashi (Ketubot 57a:) already acknowledges that in certain types of disputes one party is of necessity lying (or,to soften the implication, saying something untrue (possibly unwittingly)):

דכי פליגי תרי אליבא דחד מר אמר הכי אמר פלוני ומר אמר הכי אמר פלוני חד מינייהו משקר אבל כי פליגי תרי אמוראי בדין או באיסור והיתר כל חד אמר הכי מיסתבר טעמא אין כאן שקר כל חד וחד סברא דידיה קאמר מר יהיב טעמא להיתירא ומר יהיב טעמא לאיסורא מר מדמי מילתא למילתא הכי ומר מדמי ליה בעניינא אחרינא ואיכא למימר אלו ואלו דברי אלהים חיים הם זימנין דשייך האי טעמא וזימנין דשייך האי טעמא שהטעם מתהפך לפי שינוי הדברים בשינוי מועט

For when two (amoraim) argue about [what] one [amora] said, one saying "So-And-So said this" and one saying "So-And-So said that", one of them is lying. But when two amoraim argue about a law, or about a matter of prohibition and permissibility, each one saying "this reason is sensible", there is no falsehood – each one is saying his own resasoning, this one supplying reasoning towards permissibility and that one supplying reasoning towards prohibition. [Or] one compares one thing to another in this way while the other compares it in another way. And [in those cases] we can say "these and these are the words of the living God" – sometimes this reason is applicable and sometimes that reason is applicable, for the reason changes according to changed circumstances with [even] minor changes.