How does one prove this "Mediocrity Principle"? "Specialness" is in the realm of philosophy and from that perspective, this principle just comes across as a mellow form of nihilism. Telling students to filter all of science through the "we're not special" lens just biases them so that if there actually is something special, they will be blind to it. Might I suggest as an alternative the "Keep an Open Mind Principle"?