This Saban quote about Baldwin during Spring camp might give a little explanation.
You know after this last season I think it was realized just how far team chemistry can take these teams. Obviously coach has always known that, but the way that he openly admired that group of young men last year and how their relationships to one another were the fuel that helped keep the fire burning may have really inspired him. The council also voting for Tony Brown to leave in the post-season is another indicator.
Perhaps he's not as lenient on his "buying-in" policy as he once was. I've heard him remark something to the effect of (and I'm paraphrasing) "You don't come out here and do the right things just for you, aight? If you were just letting yourself down, that's your decision to make. But, if you come out here and you haven't bought in, and haven't put in the work and aren't willing to do the right things you aren't just letting yourself down but your hurting your teammates and all the guys who have come out here and have worked hard and put the team before themselves - and there's no place for that here at Alabama - because those guys deserve better." (end paraphrase)
So all that to say that maybe Baldwin's unwillingness to buy in and creating a toxic team chemistry could have caused Saban to say "No way, I'm not gonna let one bad apple spoil the bunch." Maybe he's placing even more emphasis than he usually does (because I'm sure it's always been a focus) on togetherness and facilitating the building of relationships between teammates.
EDIT: I'm sure it wasn't just a bad attitude that got Baldwin booted, it would probably need to be something more concrete than a bad attitude, but this idea may have played a role in it - the goal being to achieve a unique chemistry like last year's team had.