The God Embodied concept is not the same as Christianity. It is closer to Islamic Mysticism than Christian Theology. I’m not going to link to Kabbalistic sources that I do not understand. But there wasn’t anything new here. This why some anti Chabdniks call the Tanya kefira.
Shabbsai Tzvi was the first time these ideas were debated openly across the Jewish (And Muslim.) World. But it had been in the open for three hundred fifty years. If you want to ban this kind of Torah, start with the Zohar.