By abridging my right to carry a firearm for self-defense without providing adequate security against violent attacks, such businesses put me and my family at unnecessary and, in my view, unreasonable risk when patronizing said establishment. This would be akin to a business barring its customers from bringing fire extinguishers onto its premises while at the same time refusing to have a sprinkler system or fire extinguishers of its own.
This argument fails a simple logical (and smell) test. Go. Somewhere. Else.
The businesses don't put you and your family at unnecessary risk, you do so yourself by patronizing them. Go elsewhere. Why would you patronize an establishment with no fire control system that barred you from bringing your own, if fire was your primary concern?
Well, I certainly hope you don't own a business without adequate fire protection because if you do, you're likely in for a very unpleasant surprise if there's ever a fire. You can say go somewhere else all you like, but the fact of the matter is that there is copious regulation regarding businesses providing safe environments for customers and employees and I fail to see how security is any different. After all, if going somewhere else is the answer to it all, why can a business be sued when someone slips in a puddle? That person had a choice to patronize a business that didn't leave puddles in the middle of their floors didn't they?
My point here is not that I think all businesses should be legally required to allow carry, but rather that there is a distinct double standard applied to carry and other safety issues. I do not believe that "no guns" signs should carry force of law; if they don't have to recognize my right to self-defense then it should be up to them to enforce their policy. I also think that businesses which ban carry and fail to provide adequate security of their own should be open to civil liability for their unwise decisions just as they would for other safety concerns. Were this the case, I think that you'd see a lot of "no guns" signs taken down as insurance and liability is a large part of the reason that many businesses prohibit carry on their premises.
I also agree with MLeake about ignoring "no guns" signs that do not carry force of law. I've never once seen a private business that has both a "no guns" sign and armed security. Since said business obviously feels no moral obligation to provide for the safety of their patrons, I feel no moral obligation to concern myself with their asinine policy.