Only Williams isn't a Muslim. So what was the evidence? Well, that his first name is "Elijah" and that's a Muslim name. Only, of course, "Elijah" isn't a Muslim name. To the extent that names have religions, it's a Christian name. Actually, it's an anglicized version of a Hebrew name that has been assimilated into being a Christian name.
Presumably the confusion is that longtime leader (actually not the founder) of the Nation of Islam, Elijah Mohammed (who was born into a Christian family in Georgia in in 1897 as Elijah Poole) was Muslim so Elijah's a Muslim name.
"It was a bit surreal,'' Williams told the Miami Herald. "I ended up explaining to people -- some of them prominent, educated people who asked about this -- that if my name concerned them, they should know `Elijah' has Hebrew roots, that Elijah was a prominent prophet and leader in the Old Testament. But the situation was also uncomfortable.''