B"H Regarding 20a, the mishna quotes Rav Eliezer as saying, "Whoever
teaches his daughter Torah, teaches her physical intimacy." Didn't Rav Meir say in another mesechta (I can't recall which one) "Whoever teaches his daughter Torah teaches her licentiousnous."?
Is this because the bitter waters would then have no effect since she
would have merit in the study of Torah?
Rashi writes on 21b that with her knowledge of Torah she will learn to conceal her actions. The Me'iri writes that this is due to the fact that she does not fully fathom the Torah and therefore misuses it in this way.
(I am not familiar with the quote that you ascribe to Rebbi Meir (perhaps you are thinking of Rebbi Meir's statement in the last Mishnah in Kidushin?). The Minchas Yakov quotes the Metzudas David who gives the explanation that you give -- Rebbi Eliezer holds that one should not teach his daughter Torah in order that she not think that she can sin and her Zechus will be Tolah, like you write.)
D. Zupnik (and Y. Shaw)