I only partially agree. At the professional level, I don't really have a problem when coaches have different standards for different players. It's the coach's job to make the team as good as possible, and he should be able to make judgment calls about discipline, discerning whether allowing superstars leeway is better for the team, or whether doing so causes team problems which affect performance. Where I agree is that if Childress is going to have double-standards for superstars, he should probably consider Adrian Peterson a superstar worthy of the double-standard. Of course, the Vikings have so many legitimate studs, the concern about a slippery slope may be valid.
It's a dangerous game a coach plays, balancing the egos to give the team optimum performance. If Childress took a hard line on Favre's absence, and that somehow contributed to Favre deciding not to come back in 2010, the team would not be better off. But if Childress says, "Ah, hell, I'm letting Favre do whatever he wants, so I should probably go ahead and let all the other players get away with skipping OTAs too, because I have to be consistent," then the team would not be better off either. Certainly things can go wrong when the coach makes these judgment calls, and he can be wrong. Maybe he has a feel for his team and understands how players feel and respond to Favre's absence, and maybe he doesn't.
But here's the thing about the slippery slope: it's a logical fallacy. "If I make an exception for you, I have to make an exception for everybody" is a fallacy. You certainly can make an exception for one person: that's the nature of an exception.
Childress's double-standard for Favre may become a divisive locker room issue. If it was a problem last season, however, the problem did not show up in on-the-field performance. The team was very good throughout the season (I'm assuming that all those NFC championship game turnovers and the 12 men in the huddle had nothing to do with players in the locker room resenting either Childress or Favre). We'll see if it becomes an issue in 2010, but I really doubt it.