Question about knocking Yankees 1st Baseman Unconscious

[paperjam]

Yesterday the Red Sox had the bases loaded with no outs and were trailing by 1 run to the Yankees.

A double play ball was hit to Cano, relayed to Jeter who threw a bouncer to Mientkiewicz at 1st. The ball fell out of the 1st baseman's glove a split second before being knocked in the head by the runner and Mientkiewicz fell to the ground in pain and the ball rolled about 8 feet from him.

The runner continued to second and all the runners advanced a base (scoring the go ahead run).

I was surprised the commentators did not discuss this, as, had the 1st baseman not been knocked to the ground in pain, and since the ball was not far enough to allow for advancing the runners, the other run would not have scored...and considering the 1st baseman was knocked out BY the Red Sox runner, isn't it considered unsportsmanlike to take advantage of an injured player?

Yeah, the Sox won by a lot more than 1 run, but this play was clearly the turning point of the game.