I believe it was an intentional drilling of the guy, and yes, there's never a good time to do that.
Why is there even a need to brush him back? The game was pretty much over. Even if McCutchson hits a HR, there's a lefty on deck that probably has no chance of getting a hit against Chapman.
If you are going to brush the guy back throw the ball at about hip level.
Pitchers do that all the time.. no need to throw near head level like Chapman did. I'm not sure what Chapman accomplished, other then making a fool out of himself and firing up the Pirates even more.
I am pretty sure the Pirates get Leake and Homer next.. not exactly the most steady hands on the Reds staff.. although both will be well rested, since their last outings were short..