Some though experiments:
One kind of argument against citizens having guns is "what about the chance they will make a mistake with the gun and shoot some innocent person?"
This raises the question: "Who do you want making the mistakes?" The people, or the government? I vote for the people (knowing they/we will inevitably make mistakes). I prefer that the magnitude of mistakes be minimized by dispersing the power as wide as possible. When governments make mistakes with guns (Waco, Ruby Ridge, fill in your favorite abuse) they are usually much bigger mistakes than you or I could make on our own.
By the way, when individual persons make mistakes, they are held to account by the other people in the form of the government. When the government makes the mistakes, in theory the people hold them to account, but good luck suing the government! They grant themselves sovereign immunity and all too often fall into group CYA mode.
Ask anti-gunners why they don't trust you to have guns. When they say you might do something bad with guns, ask them if they would do bad things with guns. They will likely say "Of course not!" to which you reply "Do you think I am not as good as you?"
If you are debating the issue with anyone who is anti-gun, and also a member of a minority group, ask "Since you are against guns, you wouldn't mind if we took them from [their group], would you? If they have even a slight sense of history (e.g., gun control in Europe in the 1930's) they MIGHT be honest enough to say "I know how THAT story is going to end, maybe you are right." Well, maybe not.
The "you don't need that" argument. Well, unless you are buying the gun for me, I don't have to tell you why I "need" a gun, anymore than I need to tell you why I "need" the particular car I am driving or the house I am living in. This is America, at least for a little while longer. The government has the obligation to tell you why it "needs" to take things away from you or me.
Practical issues: Yes, it CAN happen here. See Katrina, LA Riots post-Rodney King verdict, hurricane Andrew, etc. Yesterday, in Chevy Chase, MD a family was held hostage during a home invasion. Not the crappy part of town, if you don't know.
Just some thoughts.