You're right; its never happened before, and it won't happen again. What you are writing is factually incorrect. The batter doesn't have to be killed to make beanings dangerous, and this one was intentional to a degree. But before you spout off again, read this article:
http://bleacherreport.com/articles/1304213-mlbs-worst-hit-by-pitch-moments-ever
As I wrote elsewhere, accidents happen. Pitches do get away from guys. The difference between this situation and all the others is that Barnes was throwing at Machado-not at his head-but at him nonetheless. I have no problem with him doing that, but he has to miss LOW, not high. He should have gotten at least 10 games for his mistake. There should be ZERO tolerance for that crap, and the penalties should be heavy, not just four games. If it were up to you I suppose we could just wait until the next guy gets maimed or killed in that situation. A clear message should be sent to MLB pitchers: you miss high there, and you pay the price.