I don't think gun owners have any responsibility to justify why they NEED the guns they have.
I strongly disagree with this. Yes, crazy people do crazy shit, no argument there. People however cannot go and readily get themselves a 747 to fly into a building, nor the material to create a bomb large enough to inflict mass casualties. Yes, anyone can make small home made bombs, though the materials to make a large bomb are readily known and monitored, hence bombs aren't easy to make to inflict mass damage.
Guns... far too easy to get a hold of IMHO. By your logic, if I came to you to buy my gun and told you I was taking it down to the local cinema and going to start killing men, women and children, apparently I have that right.
According to your logic of freedom, which is a right winged myth by the way, then I have that right. Unfortunately, there are laws... hence freedom is a myth and complete nonsense. If freedom was free, then you wouldn't be searched when getting on planes, or scanned, etc. You wouldn't have road rules, pay for fuel, food, electricity or anything else... because with freedom you can just take it.
Freedom is an incorrect aspect to include in a gun discussion IMHO, as according to your logic, a person determined insane is ok to buy and own a gun. That logic is insanity in itself.
There are lots of things that can be done to minimise gun related issues, without removing guns. Restrictions on age is a good starter, especially when statistics show a very clear and precise increase in youth gun incidents versus say those over about 26 years of age. You can makeup excuses all you want for automatic weapons, but at the end of the day they allow more carnage to be done than single shot. You don't need an automatic weapon to hunt... as a single shot per trigger pull is sufficient.
One of the largest aspects that has shown to reduce gun related incidents, is simply ensuring to own a gun you have been trained to use that weapon, passed a test on firing and maintaining it, and most of all, regular mandatory attendance at a local rifle range to keep up your weapon skills.
Guns have good and bad aspects, no argument there. You will always have bad guys who get them and do bad things with them, no argument there either. But when some young 24 year old who is studying at school and has automatic weapons and modified magazine to hold more rounds for that automatic weapon... not much good can really come from that IMHO in an urban environment.
Forced weapon safes at home for rifles has also lowered gun incidents, as guns aren't just defensive, they can just as easily be taken from your possession and used against you.... your own weapon that is.
Again, I don't see America every really accepting to restrict guns, because it is engrained within the American philosophy, which is fine if that is what you accept. It does not however negate a freedom or right under specific circumstances IMHO. This mythical freedom often preached under such conditions is negated instantly that gun laws already exist, ie. someone who has been charged with a gun offence should not have any right to own a gun.
To defend yourself when under attack is one thing, as is to use them to hunt with... but just to have an abundance of weaponry because you can... is not freedom, its insanity. I believe the US does have laws on how many weapons you can have, and their types, ie. so people don't build arsenals up. Again, US laws already negate this mythical freedom argument, along with a shitload of other laws.