How can you ignore Ramban and Rambam ?
The reason we know that j is not mashiach is because he did not effect the nevuot about yemot hamashiach IN HIS LIFETIME !
He doesn’t say because he was a meisit umadiah , [which he very well may have been]
Not getting into the משיח מן המתים discussion (haven’t voiced my opinion, don’t plan on).
Are you saying that Chachomim were okay with Christianity until Yoshe’s death!? A) All accounts show that the chachomim opposed Yoshke during his lifetime. B) The basic understanding is that B”D put Yoshke to death. Why would they do this while he was still alive!?
You insist that according to the Rambam the problem with Yoshke is only that he is a dead “Moshiach”, not a מסית ומדיח.
But here is the actual Rambam (which I quoted earlier to prove my point):
Hilchos Melachim ch. 11:
אַף יֵשׁוּעַ הַנּוֹצְרִי שֶׁדִּימָה שֶׁיִּהְיֶה מָשִׁיחַ, וְנֶהֱרָג בְּבֵית דִּין, כְּבָר נִתְנַבֵּא בּוֹ דָּנִיֵּאל, שֶׁנֶּאֱמַר “וּבְנֵי פָּרִיצֵי עַמְּךָ יִנַּשְּׂאוּ לְהַעֲמִיד חָזוֹן וְנִכְשָׁלוּ” (דניאל יא, יד). וְכִי יֵשׁ מִכְשׁוֹל גָּדוֹל מִזֶּה, שֶׁכָּל הַנְּבִיאִים דִּבְּרוּ שֶׁהַמָּשִׁיחַ גּוֹאֵל יִשְׂרָאֵל וּמוֹשִׁיעָם, וּמְקַבֵּץ נִדְחֵיהֶם וּמְחַזֵּק מִצְוָתָן, וְזֶה גָּרַם לְאַבֵּד יִשְׂרָאֵל בַּחֶרֶב, וּלְפַזֵּר שְׁאֵרִיתָם וּלְהַשְׁפִּילָם, וּלְהַחֲלִיף הַתּוֹרָה, וּלְהַטְעוֹת רוֹב הָעוֹלָם לַעֲבֹד אֱלוֹהַּ מִבַּלְעֲדֵי ה’.
“Jesus of Nazareth who imagined himself to be the Mashiach and was executed by the court was also alluded to in Daniel’s prophecies, as ibid. 11:14 states: “The vulgar among your people shall exalt themselves in an attempt to fulfill the vision, but they shall stumble.”
Can there be a greater stumbling block than Christianity? All the prophets spoke of Mashiach as the redeemer of Israel and their savior who would gather their dispersed and strengthen their observance of the mitzvot. In contrast, Christianity caused the Jews to be slain by the sword, their remnants to be scattered and humbled, the Torah to be altered, and the majority of the world to err and serve a god other than the L-rd.”