May I suggest- when someone makes a statement, rather than immediately refuting it, just say "That's interesting. Could I ask where you got that?" Then keep asking questions.
If you immediately counter it, the argument is on. If you weigh 250, I weigh 150, and you are coming at me at a dead run, I will not try to stop you. But I WILL grab your shirt and pull you TOWARDS me- probably putting you flat on your face. Example:
"This whole well regulated militia thing- everyone knows that is the National Guard." Really? Interesting. Where did you get that? Does our state define what the militia is? (hint- yours does, and it ain't the Guard) How long has the Guard been around? (1903) The Constitution was written when? (1787)
"There are about a hundred kids killed by guns every day." Interesting- did not know that- Could you show me where you saw that? The US Govt Center for Disease Control says it is 13 a day- but they are counting "children" as being up thru 24 yrs old. The FBI Crime report says 600 a year- that's less than 2 a day- not hundreds."
"All those people are being killed by criminals with machine guns and assault rifles." Yeah, I had really wondered about that. Where did you find the information on that? "Well.....everybody KNOWS that!" Yeah, I had heard that- but when I looked at the FBI Crime report, their last year showed out of 12,664 weapons used to commit murder, 323 were rifles. ANY kind of rifle. That is about 2.5%- or is my math wrong? Here- YOU look at this and see what I am doing wrong- http://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2011/crime-in-the-u.s.-2011/tables/expanded-homicide-data-table-5