As to why people respond the way they do to stories like this, I'm guessing it's due to the 2nd amendment being attacked from just about every direction and feeling a need to fight back in what ever way possible.
There is that, but there is also the subliminal insult, common to ALL minority groups who are ALL painted with the same broad brush due to the actions of a few.
All of us have the natural right to arms. Sadly, there are more than a few people who are not capable of being safe and responsible with arms.
The correct way to deal with this is to allow everyone their natural rights, and when/if certain individuals PROOVE themselves dangerously irresponsible, then THOSE people (and only those people) should have their rights restricted under due process of law.
However, that method is expensive. It is expensive in terms of time, effort, money, and suffering.
It's much, much cheaper and easier to pass gun control laws and CLAIM they work. Doing so is a degree of prior restraint on our natural rights, and is also assuming everyone is guilty without proof.
Levi (or whomever) ASKS us ALL not to bring our weapons onto their places of business. I don't have an issue with that, its their place, their rules, just as in my place, my rules. If I don't like it, I don't go there. If you don't like mine, don't visit me. Simple, and respectful.
Do note that our Constitutional rights are a matter between us, as citizens and our government. Not between us as citizens and other citizens. With the government, its something established and written. Disputes are resolved by the courts.
Between citizens (or citizens and a corporation), it is a matter of negotiation, mutual accommodation and respect (to some degree or other).
If you want someone to blame for no guns policies at businesses, (other than those directly owned by anti gun zealots) look to the insurance companies, the courts, and those idiots with gun who do stupidly irresponsible acts.