 Zamasu often questioned the worth of mortals, not trusting in their ability to handle conflict as they were prone to commence war in a repeated cycle and not understanding that mortal life was key to the prosperity of the universe.  he wants "perfect utopia"

Goku black  uses mortals as the scapegoat for his misdeeds, using Future Trunks' violation of time travel as justification for his and Future Zamasu's morally questionable goal of exterminating all life He became much more emotional 