My feelings about this exchange are well summarized by these comments at The Plum Line.
P.S. I’ll just add that if Eric Cantor had been a sane and reasonable Republican, he would have scowled angrily at this heinous remark, at the minimum remained stony faced, then forcefully denounced it. Instead, we got Cantor smiling at a deranged question, briefly stating that “noone thinks that the President is a domestic enemy” (is that the denunciation part right there?), then going on to slam Obama for, essentially, being a “domestic enemy.” Disgusting, as always. In Eric Cantor’s slimy, slippery, oily way of course.
UPDATE: Jake Tapper tweets, “so @EricCantor responds “no one thinks the President is a domestic enemy” and the @Heritage audience boos him! lunacy.”