I don't know if he is Muslim or not; but from what I see of his actions and his speeches, he prefers Islam to Christianity.
Of course, there is that slip of the tongue when talking with George Stephanopoulos...
Slip of the tongue. How often do you think someone has accidentally identified himself with "my muslim faith" when he really was a Christian? Obama may be undercover or he may just not be very devout, but he clearly and by his own word identifies with islam. That's close enough for me to know he is the enemy.