The evil thing was that, given what all humans are given, both the abilities to be good and to be evil, McCain used his life, especially at the end for assisting in mass murder. For that he deserves all our curses, but not to have his body be seen as just garbage to be burned on TV to raise funds for Syria.

And why not? He deserves all our curses but he doesn't deserve that, because it "mocks" the what the fuck? He deserves dignity, correct, and raising funds for Syria is undignified if his cadaver is celebratorly and symbolically catapulted into a pile of tires on fire?