He's upset because it trashes BOTH candidates rather than just one. See, his brain is incapable of comprehending the existence of an independent/moderate/centrist. For him, it's just ultra-liberals vs. ultra-conservatives in an epic battle that to him at least, has raged on since the beginning of time.
This is the most hilarious, (and oh so painfully true) cartoon out there!
B4e-Forever New Frontiers