The historic inaccuracy of the Mod statement is showing a shocking level of ignorance. The destruction of Alderaan was an act commanded by Gov Tarkin, not Vader.
In fact, there have been audio recordings now uncovered that demonstrate that Vader protested the attack and was over ruled.
Those same recordings go on to demonstrate that Tarkin had, indeed gone "rogue" and intended to, after Alderan, assassinate Vader and use the Weapons platform to enact a coup d'etat against the Emperor.
There is even some evidence that Tarkin was associated with the corrupt Jedi order who attempted to overthrow the Government of the republic in 19BY and had maintained contact with "old Jedi friends" such as Ahoka Tano who was instrumental in the early Rebellion.
Alderan's destruction was a tragedy brought on by 1 corrupt and rogue figure who was possibly acting in concert with a Rebel alliance of terrorists who doublecrossed and murdered him for his trouble.