I like Rush, and listen to him almost everyday... I heard this statement...and thought it was rather silly and defensive.
He's using the same carbon copy liberal cliche that anyone who doesn't agree with his criticisms of Bush, must therefore be a brain-washed robot who would defend anything Bush does.
It's a childish argument.
That only goes to his supposed divination of the motive or integrity of those who disagree with him, not to why he thinks his position his better founded than that of his critics.