Colin, you asked a direct question to which I will give a direct answer, even though the question wasn't directed to me.
Why do I need guns? Because as long as there are people who don't want to work for a living AND who don't care who they hurt in order to STEAL for a living, I need a gun to level the playing field. Not because they want to steal for a living but because they don't care who they hurt when they steal. They often don't want to leave behind witnesses. Look up the word "deterrence" in your dictionary.
In any discussion of why one needs a gun, consider the Swiss and Israelis, who have a high percentage of guns among their populations. Check their crime rates. You have to isolate acts of terrorism for Israel, but look at their domestic crime rates. Consider how many countries decided to invade Switzerland. Given the level of hatred, look at how many COUNTRIES (not terror groups, who are stateless) have decided to invade Israel and how well it has worked.
The question of "why do you need a gun" depends on who wants your land more than you do. Or your belongings. Or your daughters.