Your whole argument is that a gunman shooting up a theater, school, post office or a political rally is something that couldn't happen and the very thought of it happening makes it so we don't have to think about it. I submit that I could give you atleast 12 major incidents in the USA every year, atleast one per month of someone killing strangers while going about their day. You have to submit those circumstances of a lone gunman, with multilple weapons, shooting up a theater. Violence is one thing, a mass murdering such as this, is a different fellow. If the judge allowed it in, I don't think he would since it would have any correlation, unless you did provide circumstances of similar happenings.
Why wear a seatbelt? I don't expect or plan to get into an accident. If you get into my car and I don't allow you to use the seatbelt and I get into an accident injuring you then you have a right to hold me accountable as the car owner and driver. No comparison.....not even a good straw argument.
If I as a property owner prevent you from wearing shoes and you step on a rust nail in my yard then my insurance will end up paying; why because I'm responsible for my property and the safety of those that I have on it. The theater is no different they are responsiable for my safety, expecially when they prevent me from securing my own safety within the law all for politics and money. Just because someone is on your property doesn't make you responsible for them. This is a common misconception. However, if you had knowledge there could be rusty nails (you just tore down an old barn and had not thoroughly cleaned everything up) on the property, then you may have some liability. Trust me, your insurance company would be thinking along these same lines before making any payment.