Put down the gun – I don’t mind that the well-meaning writer believes what she believes because the lubavitcher rebbe said so. What I mind is that she thinks that her arguments are convincing or in any way meaningful to someone who does not see the lubavitcher rebbe as a primary source for all of the Jewish world. In other words, I’m not trying to convince her, I’m trying to show her how her arguments are not at all convincing on any sort of rational level.
And as far as your point about someone deciding to become a lubavitcher and changing his minhogim: it doesn’t bother me at all. But Chabadshlucah wrote that the rebbe often told people not to change their mesoira and I asked for a case where this did not involve a public relations coup, as was the case with the son of an Israeli rebbe. Perhaps there are many cases like that, but I know many Sefardi lubavitchers and not one puts on tefillin in the Sefardi manner and not one eats rice on Pesach.