Because they're total dicks?
and Steinbrenner Jr. aint his daddy. i'd guess it's a combination of what you said, they want to void his contract if this whole new PED scandal blows up (someone said it could be 100 players) and the fact that it contradicted what Cashman said the other day, so he felt stupid. Arod has done plenty to hate, but being happy for having a doctor tell you that you're healthy enough to play is not one of them.