And that is the reason the rule is written the way it is. Intent is irrelevant. The fact that Middlebrooks had nowhere to go is irrelevant. He impeded Craig from scoring and Craig would have scored if he wasn't there. That is all that matters.If you're a Red Sox fan you don't like it of course. But the fact is, if the Red Sox player isn't in the way, the run scores pretty easily.
Also, this part doesn't matter, but to those who ask what Middlebrooks could have done. How about not put himself in a place to field the ball where he is in the way? If you say Salty put him in that position, then why would Boston then get bailed out? The right call was made and the rule is in the rule books for a reason.