The ESPN guys were mocking the coach for choosing to punt in that situation, with like 4 minutes left in the game and needing 2 scores, essentially saying that the coach gave up. I can't remember the teams that played... but 2 days later and that game probably still fresh in the minds of everyone... Bronco faced the EXACT same situation and choose to punt and the Boo's rained down because...
Prior to all of this, Bronco had spoken about BYU needing to become more aggressive. He felt that it was needed for BYU to be a better program. And then Bronco, down 2 scores, decides to punt the ball at mid field with 4 minutes or less left in the game... it was the exact opposite of what Bronco said BYU needed to be.
That's why he was Boo'd.