Sure. But, if pitchers contribute a "whole lot more run prevention than anybody else", it seems to me that you'd see more pitchers winning, or at least top 3, in MVP voting. Unless, of course, you believe scoring is more important than preventing scoring.
Nonetheless, I'll get to the point. The MVP voting guidelines that some believe are "crystal clear" are anything but. They're vague. I'm not sure if that was intentional but there's a reason they vote rather than refer to one stat, let's say WAR, to determine who wins.