I would point the person to another study conducted by Harvard Law that contradicts this one. The study is called, "Would Banning Firearms Reduce Murder and Suicide". The study basically debunks any direct relation between the two. Now of course, the study that's in the story listed by the OP links gun ownership with "gun-related" homicides. Not exactly the same thing, but I would argue that the comparison itself is a moot point. It's the only way they can insinuate a link because if you compare gun ownership with all homicide rates, then the link disappears.
At any rate, this link should be shown to every anti. It was posted by another forum user in another topic. I would just post the topic...but not sure how to do that.
http://www.law.harvard.edu/students/org ... online.pdf
And a story about the study....
http://www.breitbart.com/Big-Government ... _3Fw_3D369
Original props to Bdickens.