I blame this on only having two political parties. Since each party only really has one competitor, it boils down to us versus them rhetoric.
With a viable third or fourth party, I think we'd see less "that party wants to eat your children" attacks and more stands on what they believe in. Because it's much harder to go on the attack against two or three opponents, the merits of a particular stance would have to take center stage or least get out of the back alley behind the concert where it's drinking it's cheap whiskey and crying itself to sleep.
But, for that to happen we'd need to have less of a winner takes all approach to our election system.