Whether anyone "wants" or "needs" an AR-15 or any other type of firearm, the rest of us need to know that anyone around us with such a weapon has some basic competence in using it and is responsible enough to do so. I had to pass a written and and practical test and I have to show financial responsibility to operate a car. If you can do that with your AR-15 then I won't object to your having it.

I suspect you are a careful, conscientious, and responsible gun owner and would have no problem demonstrating this, but there are a lot of people who have guns who are neither careful, conscientious, nor responsible. I hope you won't mind having to demonstrate your competence so that society can stop the other people, the irresponsible ones.

And of course, you might say that even if we had such requirement to demonstrate responsibility, the irresponsible people would circumvent the system and have guns anyway. I'm sure that's true for a few, but it would remove many guns from irresponsible hands and it would give law enforcement a reason to arrest the others and get them off the streets.