Ejected for being bad at baseball?

On Friday night, Yankees reliever Cesar Cabral faced six batters in the eighth inning, hitting three of them. After the third HBP, Cabral was ejected by plate umpire Joe West. West said after the game that Cabral "probably" did not hit the third batter maliciously, but that "before somebody got hurt, something had to be done."

My question is where West got the authority to do it. Rule 8.02(d) of the Official Baseball Rules allows the umpire to "expel" a pitcher who intentionally throws at a batter. But no one believes Cabral was intentionally throwing at anyone (I happened to watch the game--Cabral was so bad that if he had thrown at the batter, he probably would have missed). Rule 9.01(c) gives umpires residual authority to "rule on any point not specifically covered in these rules." Perhaps that includes power to ensure player safety by ejecting a player whose performance threatens that safety. (In fairness to the ump's creative rule application,  Yankee manager Joe Girardi obviously did not want to go further into his bullpen and was going to stick with Cabral to finish the inning, no matter how ineffective or dangerous he was).

Is there some other basis for this ejection that I am missing?