Omission by silence in this case would not have been diplomatic. It would have been rightly construed as a slur on one of the world's largest religions. Gratuitous kowtowing has its uses and can be effective for difusing conflict and giving the opposition no foundation for complaint.
If, as I think, Islam ("Submission") makes slaves of people, Dubya is being infinitely more eloquently diplomatic in focusing on the principles of freedom vs. slavery, and refraining from insulting -- by omission or otherwise -- the formal religion of millions of people. It appears to me that he is taking a different path to accomplishing the same thing you would rather he did by belittling Islam. Instead, he challenges ANY creed that condones slavery, oppression, and control ("Submission"), but not by name and not in a way that offends anyone's religious sensibilities -- political ones, perhaps, such as yours -- but not religious.
He plays chess, not checkers.
We appear to be fundamentally in full agreement. That works for me.