His Infernal Majesty prefers to think of his followers as responsible people who should accordingly be granted an appropriate level of responsibility. People have the right to defend themselves against assaults on themselves, their property, or their loved ones, and the Devil fondly considers his followers to be particularly deserving of both their right to exercise it and to retaliate preemptively if need be. As such, He favors their right to own and use any array of their weapons of choice.
This leads our Dark Lord to favor a relaxation of the control of deadly weapons to the point of allowing unlicensed personal ownership of weapons of mass destruction, including a wide variety of warfare material banned by the Geneva Conventions, for His devoted followers. After all, Satan represents responsibility to the responsible, and His followers being just that will know when and how to employ their arsenals, and when to (seemingly!) turn the other cheek.
The Prince of Darkness recognizes that the world is packed with people who wouldn’t exhibit the slightest sense of accountability even at gunpoint, however, and concedes that he is literally outgunned by hordes of immensely irresponsible individuals. He understands that guns should be kept out of the hands of the vast majority of irresponsible humans who incidentally, or perhaps only too predictably, are also mostly followers of His mortal foe. The Devil thinks that until His followers comprise a sweeping majority of the population, ownership of weapons should be strictly restricted and carefully controlled, and the herd should be subjected to control above trust, and razzia above control.
Satan is worried that some of His followers might be projecting their reactions, responses, and sensibilities onto people far less attuned than themselves—especially because those of His followers that oppose gun control match the demography of the aforementioned religious followers of His foe almost to a tee.