Sven Draconian
Not a Scandanavian
While much of this is true, or at least makes sense, it has nothing to do what I was talking about. My point is that you say you're differentiating between "greatest" and "best" but you're really not. When you start comparing guys' career achievements side by side to see who's the "best" (i.e. post-WWII), you're doing the exact same thing as people who are trying to figure out who the "greatest" is. If you mean the most talented and/or physically gifted pitcher, then yes it will very likely be someone pitching within the last 2 decades. When you bring in their career records, ERA, ERA+, top 10s, etc you're merely comparing them to their peers which is what people do to discern "greatest." I think that's where the disconnect is.
And you're not being entirely truthful about who was excluded from MLB in those days. There were a number of Latin players, and the occasional Native American. Granted, almost all of them were light-skinned enough to not upset the apple cart, but they were there.
To the first part, yes and no. Sandy Koufax, for example, doesn't have nearly the stats to support any claim as the "greatest", and Pedro's case is fairly weak compared to Clemens. It's a mixture of stats and observation. I think Clemens is the "greatest" pitcher of the generation, I think Maddux has a strong case for #2... but I don't think either of them were better pitchers then Pedro.
As to the second part, I would argue that the minorities that were able to play were offset by the "white" players who faced enough discrimination to be effectively barred (Immigrants, southern europeans and to an extent the irish at various periods). The overall effect on the talent pool was probably a wash.