(1) If a madman wants to kill people, he doesn't need guns. Timothy McVeigh used fertilizer. The 9-11 terrorists used box cutters and airplanes. The Nazis used cyanide gas. Every year there are many murders using baseball bats, gasoline, drugs, knives, bare hands, and many other weapons.
(2) Are we going to make fertilizer, box cutters, baseball bats, gasoline, knives, and bare hands illegal for the same reason?
(3) Just because something is illegal, that does not mean it will stop the criminals. Murder is illegal, but many people still commit murder. Also, just because it is illegal to sell something, that does not mean people will not sell and buy it. People still buy drugs. Alcohol was made illegal during prohibition and people still bought and sold booze.
(4) Many crimes are PREVENTED every year using guns.
(5) A majority of the mass murders are committed in "gun free zones". Places where it is already illegal to have a gun, but the only ones that obeyed the rules were the law-abiding citizens. The murderers didn't care about what the law said, and they continue killing until someone else with a gun showed up (police, etc.). The danger occurred when only the criminal had the gun. When additional guns arrived, safety was restored. (Did you ever hear of a mass shooting at a gun show?)
(6) Did you ever notice that some of the famous and powerful people who want to restrict guns, are themselves surrounded by armed guards? They cry there are too many guns, but they protect themselves with guns! Take Obama for example. He called for gun control, but he was surrounded by armed secret service officers. Guns protected him, but he didn't want anyone else to have a gun for protection.
(7) How would such a ban on guns be enforced?
(8) Guns don't cause murders. Murderers cause murders. If guns cause murder, then pencils cause spelling errors; cars cause speeding, and spoons cause people to be fat.
(9) The vast majority of gun owners have never, and never will, kill anyone.