Without this comment, I wouldn't have given the parent a second glance. And without that, I wouldn't have realized that "slouching towards" is a phrase I easily recognized without being able to recognize the source. So some googling (hah!) later, I found the text of The Second Coming by Yeats here: http://www.potw.org/archive/potw351.html

And it turns out, as the GP says, that Gibson is making a wonderful and highly relevant reference to the poem.