I would say Saunders and DGB are two different cases. Saunders left Fresno of his own accord and was never involved in anything that would have resulted in him being dismissed from his previous team. (as far as I know). He played by the rules of his team and the NCAA. What would other OU players have to complain about with Saunders joining the team other than more competition?
DGB was involved in two separate marijuana arrests and an assault / unlawful entry investigation which resulted in him being dismissed from his former team. If any of the players at OU would have committed the same offenses I'm pretty sure Bob Stoops would have sent them packing too. Ask Trey Metoyer. Stoops kicked him off after only one (although unsavory) incident of indecent exposure.
I'm just trying to see consistency and it isn't obvious.