“Neville, re, doing mitzvos for the sake of their rebbe”
I think I largely agree with the underlying theme that you’re criticizing, so I don’t even know why I’m about to counter this, but I’m bored…
I think it’s possible that the pamphlets you mention are singling out certain mitzvos which were singled out by the Rebbe. The proof given of the importance of Lubavitchers doing those particular mitzvos is something along the lines of “the Rebbe said so.” Albeit, maybe it would be more satisfying to an outsider if they explained the reasoning behind stressing those mitzvos in more detail, but to the target audience, it’s a good enough proof. The point is, I still think it goes without saying that mitzvos are for Hashem; even in really culty Chabad circles I’ve never doubted that. They just stress some over others because the Rebbe told them to, which in and of itself is not that unusual for Chassidim.
If I’m wrong, and the pamphlets were not talking about SPECIFIC mitzvos mentioned by the Rebbe, but rather saying the the idea of mitzvos in GENERAL is done to please the Rebbe, that’s a different story.