Is to prevent tyranny, and inherent to that, protection of life, liberty, and property.  If you dumb down the amendment to only handguns, bolt action rifles, or whatever lesser firepower may be needed to defend your home then it defeats the original intent.  Citizens have to have enough firepower to make government oppression too costly.  There is a cost to that freedom such as school shootings, suicides, etc.  How to reduce those tragedies is another topic, but the bottom line is that people who have guns at home need to secure them.  Another thing, if home invaders are bringing an AR-15 or AK to the fight I want to be able to bring the same firepower to that fight.  I'm not downplaying suicides, accidents, and other negative things that come from firearms, but positive things are pretty much always overlooked.