Well, let's show how all 4 of these arguments are not "meaningless."
4. This one I actually kind of agree with, I do say guns people, but they don't MURDER people. A gun can misfire, it can go off unexpectedly, and can be the use of somebody to kill somebody else. A gun can kill, but it lacks intent. It is just a machine, and object, it doesn't care about you nor does it hold malice. It lacks Mens rea required to be legally considered a murderer. Also, modern firearms only misfire and it only kills if the user either did a terrible job maintaining it or ignored all the rules of gun safety (as seen here: http://tvtropes.org/pmwiki/pmwiki.php/UsefulNotes/GunSafety ). The idea behind this argument isn't flawed, how it is worded is.
3. Now this depends on the philiosphy you have for the nature of objects. Yes, guns can be designed to kill people, or for target shooting, or for anti-matrial uses, or a ton of things besides JUST killing. I am of the school of the intent of the user, not the intent of the designer, is what matters.
2. Offense and defense are not that simple. Things that can do harm can be used defensively, things that can prevent harm can used offensively. Since this is a video game site, I will put this in video game terms. The Demoman's extreme defensive uses doesn't come from some high health level (he only has average health), some ability to boost up or protect allies from harm, or anything else that this cracked author considers "defensive" in the traditional sense, but his ability to do massive damage, killing the attackers before they can do anything. This would be what a defensive gun user would hope to stop. Conversely, the Medic's Ubercharge is the greatest offensive tool in the game because it allows you to push into the enemies defensive line, without them being able to stop you. A gun is also a very scary thing, and a lot of studies (I will post them if anyone wants to see them) have shown most defensive gun uses don't even involve the gun being fired.
Would a gun of stopped the Batman massacre? No, to dark, the tear gas would throw off anyones aim, and the body armor prevents most lucky shots, but many other cases these kind of things could of been prevented. Any school shooting that took place in broad daylight, none of which I can remember the shooter using body armor. There was one time where a crazed gun man locked all but one doors in a church, was carrying enough ammo to kill a lot of the people gathered there, and did kill two people on the way in, was shot in the back of the head (at point blank range) by a woman who had a revolver in her purse.
1. "Quite a debate" has only come to existence in the last century, and has been shot down again, and again, and again. For why in this ONE time would the "people" refer to a body or a group then the one which we agreed every other use of "the people" has been used? If you are suggesting we change the constitution, alright, there is a set way of doing so. The problem is, gun control is becoming increasingly unpopular, and since the amend the constitution you are required to have a super majority of the house, senate, and states all agreeing to do so, I don't think that is likely.