I think doing so at levels that are less than Division I NCAA amateur is dirty and should be penalized severely and coaches that advocate it should be barred from coaching, at those levels.
At Division I NCAA basketball, football and basketball level and professional sports level, anything is game. Money is involved and the financial rewards have to be considered. If intentionally targeting a players injury causes the other team to be more likely to lose, in a professional or Division I NCAA level, it should not only not be frowned upon, it should be and usually is the right and proper thing to do.
If Lebron goes to the basket for a lay up with his right hand and Perk or Baby or Rasheed or Garnett go to smash his elbow instead of the ball, I have no problem with that. It's why I really didn't have a problem with teams going after Perk's shoulder in prior playoff seasons. It's a weakness, you have to exploit it.