They are all EXACTLY like an AR15 in that they can fire a projectile. If you were a kid who wanted to shoot up the school and you didn’t have an AR-15, you don’t think any of your guns could be used instead? They couldn’t even be modified in some way that would allow them to be used to shoot somebody? Really?
They are exactly like an aardvark in that each weighs more than 400 grams, and yet everyone else can figure out the difference between a .22 hunting rifle and an aardvark, and everyone else can figure out the difference between a .22 hunting rifle and an AR-15. Of course, you know the difference as well. You're just creating a diversion.
The one gun I own that might cause some confusion is the Mauser. It was manufactured specifically to kill people, so if you wrote the laws badly, you might end up banning the Mauser along with the AR-15. It's a chance I'm willing to take.
There is a serious question that will have to be answered about why should one set of guns be banned and not another set. It's a worthwhile question, and I don't want to blow off any serious questions about it, so I'll do my best to answer it. First, I'm not going to go into exact detail about exactly which technical details make a gun bannable. When that's done, the legislation will be several pages long, with an appendix to define terms and a set of clarifying regulations and on and on and on. That's not someplace I'm going to go.
The short answer is that some guns make sense in self defense scenarios that an ordinary person could find themselves in, outside of their fantasy lives. i.e. That pistol really could be used to get a burglar out of your house, or to end the life of a rapist. It's a good choice for that role. Most of my guns are very good at firing at deer, where you only get one or two shots before they've bolted. Those are legitimate purposes.
You could do that with an AR-15, too, but you don't need it. The AR-15 is good for firing lots of bullets, very quickly. When do you need that? As best I can tell, you need that if you have a lot of moving targets, or you are in a fire-fight with people shooting back at you, and you need to provide suppressing fire, or you can't afford to take the time to aim a shot. That's it. An ordinary citizen, outside of their fantasy lives, will never be in a firefight, and will never have multiple moving targets. There's no good reason for an ordinary citizen to ever own that weapon. Given that no one needs that weapon, but that it can be used for mass murder, I think it should be banned for sale to ordinary citizens.
There's another serious follow up question about why we ought to allow guns that are useful in self defense or hunting, when we know that they can also be used by criminals to kill people. That is also a legitimate question, and not everyone agrees on the answer. My answer is that, whether we like it or not, we have a 2nd amendment, and the Supreme Court has ruled that a blanket ban on handguns would violate that provision of the constitution. I've read that opinion, and find no flaw with it.
I'm not sure what I would do if there were actually a movement to repeal the 2nd amendment. I could make arguments either way, that it was still necessary, or that it was outdated. However, it doesn't really matter. It's there. The courts recognize it. There's insufficient political will to even think about getting rid of it, so there it is. I, for one, am opposed to the school of thought that says that we can ignore parts of the constitution we don't like, or that we can insert parts that we think they should have included. Therefore we have the right to keep and bear arms. There won't be any blanket ban on all firearms.