Why do I need an "assault weapon?" Answer: You don't. You don't need an "assault weapon" any more than you need the right to speak freely, or the right to vote, or the right to drive whatever car you want, or the right to eat at whatever restaurant you want, or the right to protection from unreasonable search and seizure. If the government says you can only eat at one restaurant, can only drive mopeds, can not vote and can not speak without permission and can not ever speak against the government, and if the government can search your house anytime they want to... you won't die. None of those are NEEDS.
Then, ask how much they like their first amendment or fourth amendment rights? Tell them you like your second, and that the concept of freedom is not based on need- that would be communism. Freedom is based on being able to indulge in individual desires without repercussion. And also tell them that the constitution is a set of pillars upon which our republic is based... take down one pillar and you weaken the whole structure, so much so that other pillars may fall as well... or all of it could fall.
"Q"
"Our Founding Fathers, having endured the tyranny of the British Empire, wanted to guarantee our God-given liberties. They devised our three branches of government and our system of checks and balances. But they were still concerned that the system could fail, and that we might someday face a new tyranny from our own government. They wanted us to be able to defend ourselves, and that's why they gave us the Second Amendment."
Mike Huckabee