Christie has two kids that are old enough to play Call of Duty, as far as age ratings are concerned. He also has two kids that aren't old enough yet. I can understand using ratings to keep Call of Duty or other Mature games out of their hands.
As far as parents talking about video game violence goes, I do indeed think that households need to better regulate what kind of content is coming in. That goes for all media, not just games.
Unfortunately, it seems that Gov. Christie is putting partial blame for gun violence on video games. Maybe his heart is in the right place, but it's clear he doesn't know much about the topic he's looking to discuss.