The only atrocity the cult committed, was allowing ourselves to fall at the heretic's hands. With our grace, the Nords of yore were a magnificent race of warrior-philosophers who gave tribute to Alduin and the divines. They respected Alduin's beautiful children. They were scholars and pursued the mysteries of Arcana. And they were proud warriors at the same time, putting their minds into their battle-art.
The heretics were much like the Nords of today. Petty, ambitious, and eager to usurp power for themselves, and throw the common people into anarchy.
The savages commit atrocities for heretical gods, and a misguided attempt at returning to their old ways, of which they do not even know in their arrogance and delusion. They are the hypocrites here, for they villainize Mehrunes Dagon.
It is the Daedric Prince whose sphere they enact through-out their entire history since the fall of the gracious cult. Bringing forth destruction in their wake. All for the desire to conquer others. To satisfy their pride and ambition. Their lust for change. It is not Talos or Shor they should be falsely emulating. It is Mehrunes Dagon, enemy to Alduin, whom they should worship.
At least then, they wouldn't be hypocrites. But then again, Talos is a Dagonite in his own way is he not?