It is reasonable to ask whether or not it is appropriate to impose restrictions on gun ownership or barriers to gun ownership, and what those might be.
I evaluate regulating things from a default libertarian position. I think the default position should be to allow something, and the burden of proof should be on those who want to prevent or limit it.
That said, there are MANY situations where it is perfectly reasonable to limit something. Different people's rights come in conflict all the time. When they do, some rights are more central than others, and should take priority.
It's the adage of "my right to swing my arm ends at your face." Your right to life and health takes precedence over my right to move around how I'd like.
We see this principle all the time in things like speed limits and regulations on pollution or noise. Your right to travel and operate a vehicle you own must give way to the right over those around you to live and be uninjured. Your health requiring breathing clean air and drinking clean water supersedes my right to conduct business how I want. We had cars and traffic before traffic laws. Those were put in place after enough motorists had proven that they could not be relied on to operate their vehicles safely. I'm sure the number of motorists who caused problems was a minority, but the laws got applied to everyone.
Many people would argue that "It's already illegal to kill people." We can look to our traffic laws again. We could apply that same standard. We don't need speed limits or traffic laws, just punish people if they cause injury or damage. We don't do that though. We know that it is best for general public health and safety to proactively prevent damage instead of reacting to it after the fact. We give tickets for speeding and running red lights. Many places require safety inspections on vehicles to be sure they have decent tires, brakes, and signaling.
I operate a distillery. There are limits on how much spirit of >100 proof I can store without active fire protection. We share a building with other businesses. They would not want to have to wait for a fire to break out. They want to prevent a fire from breaking out. OSHA can be a PITA, but I'm glad we have it. I want to be able to tell my boss he has to take proactive steps to keep me from being injured, not let him gamble that me being injured is unlikely enough to be worth the risk that it could cost him money.
I presume this makes sense and that the vast majority of people here would find these standards to be reasonable.
How do these standards apply to firearms?
Firearm owners have a right to private property and to use it as they like and enjoy. However, we see this right to own items like guns conflicting with the rights to life and health of other people. The right of those children to live supersedes my right to own a gun.
I am a responsible gun owner. I am not the problem. Other people are. But a fair number of people in the general populace have demonstrate that our existing gun laws are sufficiently open to allow preventable damages to other people's rights to life and health.
It is not sufficient to wait for people to demonstrate they should not own guns. Just like we don't wait for people to prove they can't safely operate a car. It is reasonable to change the requirement to be on people who want to own a tool designed to project deadly force at a distance to demonstrate that they can safely and responsible own and operate such a tool.
Yeah... I know this is a lot easier said than done.