Dear Mdd,
Those are one liners. The Rambam wrote many chapters on theory and two major essays on belief.
What does kiddushin prove? If one is mikadesh his sister there is no kiddushin. Obviously they must be out of the fold.
I am ignorant of so many things.
The fold here is that being Chabad has the same din of any other Yid. I thought that was a settled matter. There are some safeguards on using their geirus etc. that are put in place by Chabad itself. So obviously we trust them. What is the purpose of slandering them?