It's kinda like when bateman's spotter is helping him do bench presses. They're both wearing short shorts and the spotter's junk is right in bateman's view. As bateman struggles to get that last rep in, the site of his partner's bulging package and the anticipation of "hitting the showers" allows him to muster up the strength to finish the rep.
superman is bateman.
the earth is bateman's gay lover.
the large kryptonite rock is the bench pressed weight.
you get me?