The only thing I can't be sure of is if the politicians themselves are this scared or if they're just playing on the fears of voters. I imagine its a little of both. They share many of the same fears as their base such as brown people, gays, and 'socialist medicine'. So they know how to lie and exaggerate to whip the fringe into a frenzy of fear and hate.
Obama's bow is the act of a man of confidence. The screaming from the crazies is the mark of fear and weakness.