...was awesome last year and nothing needs to be changed? The defense was below average, the offense was abysmal starting from the OC to the QB on down. If he

Saying you're going to do things differently and one of those things is you're going to have the QB compete for his starting job isn't throwing him under the bus. Competition is good and brings out the best in all of us. Early in Bronco's career as HC he stated frequently that guys would have to compete daily in practice to keep their starting spot and to keep their spots on the 2 deep. If a player didn't bring it every day to practice he ran the risk of letting a backup steal his spot. There's nothing wrong with that. Sounds like Tanner has accepted that challenge so I don't know why you and others are having a hissy fit over it.

Facing a little adversity is good for a person. A player either has no heart to continue and they quit (in which case didn't they already quit prior to getting to that point?) or the player gets a chip on their shoulder and forms a resolve "I'll show you!". Any time you get yelled at in practice or on the sideline of a game in front of 60K fans for screwing up you're getting publicly held accountable.

In 2014 Bronco threw his entire defense under the bus in his rush to defend his boy wonder (Nick Howell) when the defense was revolting during the 4 game losing streak mid-season. The defense responded and the team went on a 4 game win streak including a road win over Cal to close the regular season. Sometimes it's called for.