Bias and the "Science" of History

In a recent comment thread I was accused of "the greatest bias imaginable" because I have denied that "Bush's handling of the GWOT is not falsifiable". In that thread, DarkSyd had asked me,

And Bush is the guy making the decisions, so he's the guy responsible from here on out. So another major attack, and Mark Olson admits Bush taking what little heat we had on off of AQ/OBL and directing our resources into Iraq was a bad idea and starts stating it publicly on this Blog, right?

I had replied in short (full reply here) that I could not admit as such because we don't know what would happen if events were replayed and we didn't invade.

His short retort back was that this was dirty pool and by not being able to admit Bush made a mistake, I'm something of a fool.

I think not. History is not like physics. if we do X and Y occurs. We can't reset and re-run the experiment to see if by not doing X, will Y not occur (or occur sooner, later, better or worse). Decisions made by world leaders are almost never "falsifiable". For example, Churchill was one of the great leaders of the WWII era. Historians can quibble about his strategic decisions, but can they show that any of his decisions were "falsifiable"? No. I don't even know what that means. And even if some of his decisions were seen to be a mistake right after he committed them, does that mean that the Brits were wrong to continue supporting him? No. Does that make them "biased". Well, yes they were biased. But I would preferred the term patriotic. I guess I'm just that kind of fool. :)