Avoda Zarah - changing

     Sanhedrin (29a) R. Samuel b. Nahman said in R. Jonathan's name: Whence do we know that we do not plead on behalf of a Mesith? — From the story of the ancient serpent. For R. Simlai said: The serpent had many pleas to put forward but did not do so. Then why did not the Holy One, blessed be He, plead on its behalf? — Because it offered none itself. What could it have said [to justify itself?] — ‘When the words of the teacher and those of the pupil [are contradictory], whose words should be hearkened to; surely the teacher's!’

Rabbi Avraham Auerbach states there is an obvious problem. The din of mesis only applies to Avoda Zara- so how can it be relevant to the deeds of the Serpent? In Peschei Avraham he explains that originally all rebellion against G-d's will was considered AZ.After Adam sinned the laws of AZ became what we see in the gemorah