"Walking Barry Bonds with the bases loaded was never a good decision. Ever."
I assume,JH, you say that because you believe you know (illogically, I'd say) that there were absolutely no other variables, beyond baseball stats, that could have impacted the outcome?
But what if, hypothetically, the manager knew that the next guy up had a fractured wrist ... or a post-game appointment with the police who intended to put him in handcuffs ... or, God forbid: Hemorrhoids?
Would any of those situations make walking Bonds a good decision?
Not statistically, I suppose.
But aren't there an infinite number of variables that should influence managers' decisions? Up to and including, maybe -- streaks?
I think the cocoon you're weaving and getting trapped inside is putting complete faith in numerical data. It's a game played and coached by humans, right? And that just obliterates a whole lot of stats.
In my experience, great leaders use data but never rely on it.
(silly examples, but only to make a point) 
Walking Bonds could be a good decision if Mayne owed money to LV bookies and was throwing the game, sure. I mean if you want to make up completely ridiculous hypotheticals I'm sure we could come up with some scenarios where walking Bonds had a positive expectation.
But in the absence of any evidence for any of those hypotheticals, there's no reason to give them any weight in analyzing the situation. And since we have plenty of evidence that "hot streaks" and "clutchness" don't actually exist in any way that's exploitable on the field, there's no reason to give them any weight either.
Here's something I'm sure will just make this argument worse. Results don't matter. Making the best possible decision given the available evidence (and I mean that word in the most concrete possible sense) is all that matters. If you throw Barry Bonds the perfect pitch for getting him out, and he hits a HR anyway, it doesn't matter, because you gave yourself the best possible chance to win. If you walk him, you haven't given yourself the best chance to win, and if you happen to win anyway, that doesn't make your decision better, or right, after the fact.
If you play baseball (or manage it) long enough (or really do anything productive), and you aren't always making the best pitch, or taking the best swing, or making the best managerial decision you can, you're leaving money on the table, and someone else will benefit from that. If you aren't constantly reviewing the processes you're using to be the best you can be, you're going to miss the opportunities to correct your shortcomings, and someone will eventually come along and eat your lunch.