The trouble with your point is that it is TOO realist about "Islam" as an entity. When someone says, "Bin Laden has nothing to do with real Islam", they are not making an empirical assertion. They are engaging in a speech act. They are saying, "Muslims ought not to engage in violence against innocents, and those aspects of the Islamic tradition that assert this should be emphasized in comparison to those which do not."
Saying this speech act is false is like saying "give peace a chance" is false (or "unite against the oppressors of our people" is false). It is a category mistake.
The real objection to Bush is that "Bin Laden is not a true Muslim" is a speech act only available for an insider.
As Uncle Karl would say, "The non-Arabic-speaking bloggers have interpreted Islam in various ways. The point, however, is to change it."