I’ve heard the arguments a million times.
Those in favor of the DH say that you generate more offense, which fans like to see. You can extend the careers of good hitters who have slowed down and become a defensive liability later in their careers. You don’t kill a rally when you see the pitcher come to bat, and he’s an almost automatic out.
Those against the DH say that everyone who is playing should have to hit also. These people enjoy the strategy such as the double switch in the National League when a relief pitcher comes in. They enjoy the strategy involved in when you change pitchers, keeping in mind that the pitcher’s spot in the batting order may come up next inning, and you may have to pinch hit for the pitcher you just brought into the game.
I’m sure there are other arguments, but these seem to be the ones which come up a lot.
You can extend the careers of good hitters who have slowed down and become a defensive liability later in their careers.
They found places for those players before the DH -- Dick Stuart and Pete Ward are good examples. And their defensive liabilities helped keep things interesting.
You don’t kill a rally when you see the pitcher come to bat, and he’s an almost automatic out.
Like Doug Fister's double yesterday.
The pitcher usually only bats twice a game anyway, and they can be taught to bunt or do something else that is productive for the offense.