I don't think McDermott is trying to "protect his defense" so much as he has a certain philosophy that, if adhered to strictly, will usually result in a win.
There's a lot of bad football being played every week. Anyone who watches games around the league sees that. So the strategy works most of the time.
Add in a talent like Allen and it works even more of the time.
But against an elite opponent, who doesn't throw the costly int and can stay disciplined enough all game to take the small stuff it often does not work.