Whether it's Heaps vs. Riley or Tanner vs. Taysom, what kind of ego do you need to have to decide that Kalani and Detmer and their years of experience are idiots and just don't get it? Not to mention the fact that nobody studies practice reps or game film more than they do.
Seriously, you have a coach willing to call a fake punt out of his own endzone, but isn't willing to play QB roulette. There's a reason for it and CB is not entitled to know why. This is no knock on Mangum as I look forward to seeing him take a lot of snaps in the future. But I wouldn't begin to question the coaches decision on playing time come game day. Let 'em do their job.
If you continue to feel the urge, go volunteer to coach recreational leagues and make all the decisions you want. Maybe it will help you understand that it isn't as cut and dried as you've made it out to be on the anonymous interwebs.
Rant over ... flame away.