I didn't write this
This comes down to a pretty fundamental principle that is at the very, absolute core of the American identity: The supremacy of the individual over the state. This manifests in different ways and gets interpreted in others. This is at the heart of the conservative/liberal, urban/rural, and literalist/non-literist camp of the Constitution.
The obvious ones on which there is general consensus is freedom of expression, of action and of faith so long as it doesn't inhibit another's right to the same. Others are pretty much agreed on now though they took some time to get there: equality regardless of race or gender. All of these so far are easy to reconcile in both sides of the American identity because it fits well in both.
It becomes murkier when you start including tougher concepts like "public good" and individual responsibility. Who is entrusted with ensuring the public good? Is it the collection of individuals or the government they form? Who is responsible for the people's prosperity? Is it the government or the individual? Healthcare, Education and in this instance, security/gun ownership is at the heart of who is responsible for their own welfare. To the left, its easier to give that responsibility to the state, as its supported by a consensus (vote). To the right, this is seen as a dangerous step that can very easily lead to government that simply cannot be overcome.
Keep this principle in mind: The government serves the people, to those on the left: the vote ensures that. To those on the right: the ability to resist ensures that. Gun ownership and its defenders fall back on one principle: the government must always be afraid of its own people in order to prevent it from overstepping its bounds and infringing on the supremacy of the individual. To put it bluntly, many in America hold very close to their beliefs that Americans withhold the right to overthrow the government at any time. This was an argument at the heart of the Civil War.
So why do Americans still accept gun violence? How many more Columbines? How many Sandy Hooks, Virginia Techs, Las Vegas? How many people have to be murdered until we begin to trust our own government with what many view; as absolute power? Never, maybe. I can't in good conscience say that gun laws as they are make sense, or that who is getting them should have any access at all, but this isn't as simple as 'take the guns away'.