I first will commend the author for making a great argument for her position. All her points deserve consideration. However, I am not in agreement.

Legally speaking, this same situation can be framed into similar yet different scenarios. Just exactly where is this line for the "right to one's defend property or life"? I'm not confident that the courts can sort this out well enough for a significant majority of the people believe the decisions are made with good principles of justice. And many of these decisions will be made based on what side of the political divide the perpetrators (and juries) belong to. In other words, there is just a really big fuzzy area of right and wrong.

Practically speaking, confronting any protest is risky. Yes, a property owner's presence with a visible gun might deter protesters from vandalizing your property. But the same stance will also make one a target for the more anarchist of protesters.

There is a whole psychology when a mob gathers in anger. Normal thinking people can become kind of stupid in these emotionally charged mobs. And some protesters see the opportunity to "do bad" and probably not get caught because so many other people are "doing bad." To somehow believe someone with a gun (or a few someones with guns) can actually thwart vandalism on a consistent basis is begging for something to go wrong. Sorry, preventing a business from being vandalized is not worth my life. I don't feel sorry for anyone who takes the law into their own hands--even if the police will not likely be able to arrest the actual perpetrator(s) in these kinds of situations. It's not always a fair world, is it?

Another factor is that most people will not encounter this protester kind of situation in their lives. It is more likely that most of us will be involved in a serious auto accident than face down protesters who could damage our property. Most of us will have several close calls with auto accidents in our lives. In other words, defending property against wild protesters is a very low probability bad event.