In terms of civility and respect for the office of the presidency (not necessarily the individual occupying it), this reminds me of the infamous "you lie" moment during a speech that Obama delivered to Congress regarding healthcare reform. Joe Wilson, a House Republican from South Carolina, essentially heckled the president, but his comment generated so much heat from liberals that he subsequently issued a formal apology. Much of the liberal commentary accused Wilson of inappropriate behavior and racism.
I doubt that the House Democrat's outburst will generate the same reaction. First, the person remains unidentified. Second, liberals probably do not want to bring attention to their own lack of decorum or, even worse, racism. C'est la vie.