Final answer:
The least useful detail for supporting the claim that gun control laws will not stop further gun violence is option D, which discusses the complex motivations of killers rather than the direct impact of gun control laws on the ability to perpetrate such violence.
Step-by-step explanation:
The detail that is LEAST useful for supporting the claim that gun control laws will not stop further gun violence is option D: Reducing evil to an object without addressing the complex motivations that drive killers to commit unspeakable acts serves no purpose other than padding political talking points. This statement is less about the effectiveness of gun control laws and more about the discussion around the motivations behind gun violence, which may not directly support or refute the effectiveness of gun measures. In contrast, option A refers to the situation in France, which is a comparison between different countries' gun laws and the occurrence of mass violence; option B points to the specifics of the Las Vegas shooting and the killer’s tactical advantage, which could imply that gun control may not have been effective in that scenario; and option C suggests that armed response might be an alternative to gun control for ending such attacks faster.