Before President Obama had even made his deficit speech, Congressman Paul Ryan spelled out his concerns over its impact. On Sunday, he accused Obama on Fox News of launching "class warfare" by introducing the so-called Buffett Rule. The president rebuffed the remarks saying "This is not class warfare. It's math."   Ken Davis, author of "Don't Know Much About History: Everything You Need to Know About American History but Never Learned," talks about the history of class warfare.