[@BCTheEntity] Uno question, por favor!

If a member of the Zodiac Guard is more-or-less more than a match for a Primarch, if say...I dunno...a Primarch was to initiate some sort of...let us say...civil war, for whatever reason or motivation, then couldn't the Emperor just send an Armatus to rip them apart in what would seem to be a pretty simple way? Therefore sort of nullifying any moitivation one might have to intiate said war?