Because he's claiming he's never been one when he knows better. He was born a Muslim and given a Muslim name.
This is very personally insulting.
Having an Arabic name myself, I reject any notion of a "Muslim" name by default. There was Arabic culture and names long before Islam came around. I am not Muslim and will likely never be a Muslim despite my "Muslim" name.
Does biggotry know no bounds?
Of course, biblical creationists are committed to belief in God's written Word, the Bible, which forbids bearing false witness; --AIG (lest they forget)