For what it's worth, here's what I think... And I wrote briefly about this on the old Mater site, but it was right before they pulled the plug so I don't know how much 'air time' it got.
It's about loyalty, plain & simple. Has anyone heard the saying: "Praise in public, but punish in private"? There's purpose and simple logic in that statement.
If Don, or anyone who owns and operates a team for that matter, doesn't support his team publicly - and that means each and every member of it, they, in turn, won't support him. That's leadership 101 folks. Your people have to know you stand behind them, even when they're struggling.
Look at the way he handled the Ron Capps/Whit Bazemore issue. I, for one, was thoroughly impressed. They've raced each other twice, very recently, with Whit winning both times and yet they remain cordial in public. Sure, they deserve credit for being professional, but don't think for one minute that Don Schumacher didn't have a lot to do with that - privately.
Also, remember back to Seattle when Scelzi was "directed" to take the bad lane so Whit could stay in the hunt - Don Schumacher publicly accepted responsibility, effectively relieving his team(s) from taking any of the heat. They've raced heads-up ever since & it's been awesome.
Additionally, none of us know the details of the contract between DSR & Mopar. Don and his drivers & teams have a responsibility to support Mopar's (or whoever's) desires or he risks losing their backing. Again, leadership 101. If you're willing to publicly go against the wishes of your leader(s), what makes you think they're going to continue to support you? They won't, plain and simple. It's true in relationships, it's true in business & it's true on the battlefield. So if Mopar, as it's been theorized on this site, wanted Shaun in the car, then Don did exactly what he had to do & I respect him for it.
I'm not necessarily a big DSR fan, but I don't have anything against him either. Nor am I a huge fan of multi-car teams. And personally I don't think Shaun was the right choice to drive the (at the time) 2nd DSR Pro Stock car - but I ain't signin' the checks so my opinion don't mean squat. All that aside, I commend Don Schumacher for his leadership and management skills under some fairly stressful conditions. He did right by Shaun Carlson & Mopar... and yes, even Bob Glidden. He never said a negative word about the man, and in fact, holds him in high esteem.