Matthew Dollof, the shooter, was
charged with 1st degree murder today and is being held without bond. A Denver prosecutor and a judge didn't think it was justified.
While, I disagree with you on principle I agree that in some states, Florida, for example he might not even be charged. The legal precedent in this country, going back almost 200 years is "no obligation to retreat". Our principle of "no obligation to retreat" is at odds with most nations. It is one of the peculiarities of the US legal system. It also affects the way we react when the flight or fight response elevates.
You are jumping to the side of the shooter when earlier you were "castrate all men" because we are all such violent goons. Gender profiling is about as biased and bigoted as racial profiling. Both simply reflect the ignorance and bias of the person doing the profiling.