I hesitate to use Wikipedia, but here's a source that appears to be fairly well documented and supports what I wrote. https://en.wikipedia.org/wiki/Defensive_gun_use
I agree that the defensive use of an AR-15, or any rifle for that matter, is rare. Handguns are heavily favored. However, if defending a home, a rifle, including AR-15s can be made readily accessible and is highly effective. As to accuracy, a rifle, AR-15 included, is far more accurate due to the significantly longer sight radius; the distance between the front a rear sights. Semiautomatic rifles, such as the AR-15 are capable of firing many bullets in a short time, just as are semiautomatic handguns, caliber 9mm parabellum specifically, that commonly are equipped with magazines that will hold 15 to 17 cartridges. There are some extended handgun magazines that will accommodate even more. The AR-15 is a very popular rifle used in various ways and rarely in mass murders. So why penalize the many for the acts of a few?