That's how corporations are, they fire anyone who does anything that could even potentially lead to a lawsuit.
It's actually pretty funny how these corporations hire the most expensive attorneys money can by to defend them in court, yet go out of their way to avoid using them, even if it only results in exposing them to yet another potential lawsuit in the process.
That's why nobody should ever expect loyalty from their employers, they'll sooner cut you loose than defend you because in the end, all they care about is money.
I think their legions of lawyers are often for contract and other similar civil law concerns. Suing people and businesses for breach of contract, reviewing contracts, legal notices, ect. Their main job is not sitting around waiting for the families of dead thugs to launch lawsuits, or answer every ambulance chaser who tries to make a ticket over an injury in a parking lot.
The sad state of affairs with law is that it is so expensive to defend yourself, it is oft advised to "just settle, still cheaper than winning", which leads to the very worst of lawyers winning in many cases where they don't have merit.
Sometimes principle, or setting an example to stop predatory lawsuits, means they will stand and fight, especially against the most obvious baseless claims. But, sometimes it is easier to throw them a few bucks and make the whole thing go away.
I think the entire problem in this particular case is that it truly is "an ounce of prevention is worth a pound of cure". By simply making the policy AT ALL, they will oft make themselves nearly immune to a lawsuit, by setting a company policy in the first place. When an employee uses a weapon in self defense, they can claim to have washed their hands by simply having a policy against in the first place, meaning the employee acted on their own will against the company.
Even if the management team at the company agreed with the employee and thought she did the right thing, they will still opt to simply fire her and reinforce their policy to mitigate liability. So the next bandit who gets greased on company property is not their problem.
I can understand the animosity towards the company. On the other hand, i understand the current sad state of civil law in the US, and how much bad lawyers cause harm to society through tossing lawsuits at the wall to see what sticks.
The first step to fixing this is tort reform. Something we will never get.