I don't even know that I want to mention this but here goes:
I don't believe in throwing at somebodies head either. There have been particular nut case pitchers over the entire long history of baseball that have thrown at the head but they are so rare its not even worth talking about. Usually pitchers that hit somebody in the head are throwing up and in and a pitch gets away from them. Its not intentional, virtually never intentional especially in the modern era.
Having been drilled in this particular spot before, if a pitcher wants to send a message and stay completely away from the head forget hitting the player in the butt. If you get drilled in the side under the heart or around the liver (depending on what side you bat from) it takes your breadth away. Been hit there more than once and and even if you are not hit just right, if you are drilled it really hurts. The boring two seam inside tends to get under the arm and into your rib cage and you can't get out of the way of it because it keeps boring in on you. If you are drilled just right and it does take your breadth away, you think you are going to die for about a second. But, you will be OK which sort of is the idea right. You will however know you have been drilled for a couple days afterward. The pitcher is truly "sending a message" with that pitch. You are for the most crawling not walking to first base to take your base.
But as I have said before, Manny is a different case. If the team he plays for keeps playing him at Short given Manny's antics around the bags and with the bat, some player might be just crazy enough (as crazy as Manny is) to get him that way. Somebody is going to careen not into the blocking leg at 2nd base but into that locked knee he hangs out there that he is no longer agile enough to get out of the way. Completely legal slide based on today's rules.