I’ve put together a compilation of articles and essays regarding why to own a gun. Most of these include sound reasons for gun ownership and will possibly give you the ammunition needed to win an argument on the benefits of gun ownership. More importantly, this may give you the reasons you might need to arm yourself.
Here is one of the best philosophical arguments I’ve seen that mirrors my own beliefs and encompasses some of the best thinkers on the subject of personal rights and duties as applied to gun ownership. Why the gun is civilization.
Here is another one from Calguns on why guns are necessary for a civilized society.