My argument isn't that pitchers are below average so they should be replaced at the plate. It's that they are so bad, that their performance doesn't even rise to the threshold of acceptable.
BTW, those trying to take this to an extreme regarding offensive specialization (i.e. replacing position players at bats with the DH), seem to ignore that pitching staffs have already evolved to a level of specialization that is well past what proponents of the DH assume would be the logical use of a DH (i.e. batting for the pitcher). Also, it's not like NL rosters haven't carried defensive specialists to serve as late inning defensive replacements or pinch hitting gurus at the ends of their benches.
The concept has been embraced as part of the NL fabric for forever. I'm not sure why so many so easily take the notion of the DH to an extreme when arguing against it.
I get that alot of people are traditionalists. I get that alot of people like to bite their nails pondering what Dusty will do with Cueto in the bottom of the 7th. But I don't get acting like the evil AL is plotting to force the NL to bat Adam Dunn 9 times in a row or that the DH would alter baseball into some unreconizeable game that might as well be played by robots.