Here's more from Rabbi Menken:
This is why one might note a difference between changes in the service as part of a school of thought derived from Kabbalah, vs. changes in the service as part of a school of thought derived from Enlightenment-era Protestant Christianity. One is Jewish, and one isn’t.
I see. So, the kabbalah fell from the sky perfectly intact, and was never in any way influenced by the outside? Odd. Because according to people who have, y'know, actually studied the Kabalah literature the outside influences are obvious. As one example, take the Zohar. It contains:
1 - names of rabbis who were born after Bar Yochai had already died;
2 - ritual observances which were ordained by rabbinical authorities who were born after Bar Yochai had already died;
3 - mentions the crusades against the Muslims (who, inconveniently, did not exist in the second century); 4- uses the expression "esnoga", which is a Portuguese corruption of "synagogue;"
5- gives a mystical explanation of the Hebrew vowel-points, which were not introduced until long after the Talmudic period.
6 - contains suspicious marks of Spanish and Spanish sentence patterns
7 - is riddled with Aramaic errors; at times, Scholem found, the Aramaic is actually Hebrew with a few extra alephs scattered here and there.
Moreover, Yitzchak of Acco, student of the Ramban, reviewed the Zohar manuscript, and determined that the Zohar was, in fact, written by Moses de Leon. (See Sefer HaYuchasin by Rabbi Avraham Zacuto 1425- c. 1515 CE in which Mrs. de Leon admits the fraud.)
All of this is evidence of the "outside influences" Rabbi Menken disdains.
In short, R. Menken is badly mistaken when he imagines there is something inauthentically Jewish about accepting ideas from the outside. We've always done it. The evidence is everywhere-- and often written in large letters on our books, our rituals and our beliefs.