Why do the allusions to whitman in galway kinnell's "vapor trail reflected in the frog pond" create tension?

The old watch: their thick eyes puff and foreclose by the moon. The young, heads trailed by the beginnings of necks, shiver, in the guarantee they shall be bodies. In the frog pond the vapor trail of a SAC bomber creeps, I hear its drone, drifting, high up in immaculate ozone. 2 And I hear, coming over the hills, America singing, her varied carols I hear: crack of deputies' rifles practicing their aim on stray dogs at night, sput of cattleprod, TV going on about the smells of the human body, curses of the soldier as he poisons, burns, grinds, and stabs the rice of the world, with open mouth, crying strong, hysterical curses. eyes crinkled shut at almost seeing the drifting sun that gives us

They were both presidents.