"Why do you need an AR15?"

[stanc]

How can you define an assault rifle as either offensive or defensive? If I'm using one to clear a compound, then it's an offensive weapon. If using it to keep someone else from getting into my compound, then it's defensive. How it is being used defines this, not any physical characteristic of the weapon itself.

Most (if not all) weapons can be used in either offense or defense. But, rifles are primarily offensive weapons, whereas handguns are mainly defensive.

An AR-15 is by definition not an assault rifle.

True, AR15s commonly available are not technically assault rifles.
However, that's really a distinction without a practical difference.
Military SOP is to use semi-auto fire only; full-auto is rarely used.
A semi-auto AR15 with 30-rd mag is just as effective as an M16 that is fired only semi-auto.
Plus, as was seen in Las Vegas, a semi-auto AR15 can be legally altered to emulate full-auto.

The government does not decide what rights we have or don't have. The constitution and bill of rights have already decided this.

LOL. Who do you think wrote the Constitution and Bill of Rights? Hint: It was members of the government.