Additionally @grass,
Isn’t the tayna you bring above more a tayna against all chassidim of all kreyzen? Given that all chassidim base their Judaism on the word of “one person” as you say? How is Chabad different in this than Breslev or any other chassidishe kreyz?
Also technically speaking, in Chabad we base our shitos in Judaism on the beliefs of 9 people, given the Baal Shem Tov, the Magid, and all the Rabbeim.