There's an argument that having "murder at your fingertips" can make a law-abiding citizen more likely to become a killer in a fit of rage.
If this theoretical argument is by itself sufficient to justify the ban on firearms, then it can also justify banning kitchen knives. To take this argument seriously, we need statistical evidence that gun ownership by law-abiding citizens significantly increases the number of such killings. Your example of Switzerland suggests that this may not be the case.
