How can people speak against a group keeping the minhagim of their Rebbe?! The Lubavitcher Rebbe Zatzal was an Odom Godol. He paskened for his chasidim, and therefore they are obliged to follow.
Someone once said, The mishna brura is for baalei tshuva and geirim, meaning that if you have a mesorah and an established minhag, you follow that even if it may be contrary to the accepted halocha. Minhag Yisroel Torah.
For example, as Yekkes, we go by the psakim of the Maharil, who was before the Shulchan oruch. Therefore you may find an Ashkenaz shul with a minhag to daven mincha after shkiah. Now, most people don’t know that, and it is contrary to the mishnah brura, but that is the minhag.