Now, my DH is a former pitcher and he is all about protecting your teammates. You hit one of our guys, we get an opportunity to hit you back. End of argument. I agree with this somewhat, but am completely against "head hunting" (when a pitcher intentionally throws at someone's head - see Roger Clemens controversy involving Mike Piazza.)
To illustrate my feelings on the subject, I offer this pictorial:
See this guy ? He is the Angels best player. Not the best target if you don't want to start something.
No. Seriously. This is your warning... Don't mess with our best player.
OK. Now you did it. We get a "hit" in return.
Ready? Here is comes!
OK. Tit for tat. This should put an end to it.
Oh no you did not!
OK Boys, let em have it!