I've gone back and looked at this thing a few times now, and I see it as less of a dirty play and more of an oh crap play.
It looks like Utley had committed to the slide, and was anticipating Tejada to be further away from the bag. Usually a MIF will be moving away from the bag on that type of play - but Tejada was actually moving into the bag. I'm not in Utley's head, but it looks like he intended to do the traditional reach back with the left arm, while sweeping the fielder's legs with his extended right leg. When Tejada closed the distance between them, Utley didn't get the chance to extend his legs.
Of course this is all a result of MLB allowing the MIF to get taken out, but I think the severity of the collision was more of a miscalculation than anything else.