The MVP rules explicitly say that pitchers are considered fair game.
Starters pitch fewer games but have much more influence on the games than a position player. It is hard for a pitcher to deliver MVP level performances - but they can. Verlander did when he won. Now the Eck, Willie Hernandez atrocities are a different kettle of fish.
And remember, when Pedro lost, two voters did not put him on the ballot due to feeling that pitchers have their own award. They violated the rules of the award by not considering pitchers. If you did not think Pedro was a Top 10 player that season you have left your sense.