So, let's do the math. He would likely have had 4 more starts, max. Perhaps if we clinch the division, he could have been skipped for his final start. OK. now assume we make it to the World Series, he'll get another 3 starts, at least, possibly four. It could be as many as six more starts in the playoffs.
If we add 9 more starts, at six innings per start, that would push his innings count up to 213, for a 24 year old pitcher who's never pitched more than 123 innings. How is that responsible management?
And if you're not going to let him pitch to the end of the season, whenever that happens, how would his reaction be any different then than it is now?