That seems to be a popular question from the anti-gun crowd. The question is a trap. It includes a premise that must be rejected.....that rights are based on need. To quote Thomas Paine from RIGHTS OF MAN: "Natural rights are those which appertain to man in right of his existence" and "Civil rights are those which appertain to man in right of his being a member of society". If you believe that the right to keep and bear arms is a natural right, then it is not and cannot be based on need.
First you should ask them if there were items that kill more people every year than firearms, if they would deem it neccesary to remove them from civillian possession, and then you go into the questioning below.
Ask them why they need a vehicle. Then inform them that vehicles are responsible for more deaths than anything in this country. Then ask them if they find it moral and neccesary to ban them from civillian possession so we can save the tens of thousands of lives they take each year. Being as they are serious death dealers, wouldn't it be better to walk than to kill all of those people?
Ask them if they believe this country is better because of physicians. Then inform them that medical mistakes kill more than 100,000 people every year in the United States. So, shouldn't we prohibit doctors from "possessing" patients since they kill so many of them each year -- many more people than firearms do.
Ask them if we need prescription medication. Tell them this kills more people every year than firearms, so we should ban all prescription medication from civillian possession.
Ask them why they need an iPhone or an alcoholic drink. Ask them if they believe we should go back to prohibition to save the tens of thousands of lives alcohol takes every year -- many more than firearms.
Ask them why they need anything. Ask them why they need a seat-belt or a fire-extinguisher. Ask them why they need car insurance or life insurance.
We need it for self-defense, hunting, sport, 3-gun, etc., etc.
We need it because we want it. Why is it any of their business? We could ask the same thing about numerous things they have I'm sure.