Leaving open the question: why accept the Tanakh, since it, or at least those who clung to it, were anti-Christian? Council or not, Jamnia at least symbollically marks a break between Jews and Jews--between those who accepted Jesus and those who didn't. So far as I can tell, the Talmud seems to be the work of men who didn't believe --much--in Messiah. or at least were trying to distance themselves from Christianity as an ideology.
You don't seem to get it. The Hebrew Canon was set one century before Christ. Whatever the Jews thought of Christ one way or the other 100 years after the canon was closed is irrelevant to the content of the canon. The work itself is not anti-Christian and is actually quite the opposite. Your premise seems to have evaporated.