In actual fact he was a member of the Luo tribe of Kenya, who are based on the west side of the country farthest from Arab/Muslim influence.
The Luo are not Arabs, they are Bantu blacks, though of course there could always be a Semite somewhere in the family's woodpile.
I think this attempt to parse a candidate's "bloodline" to determine "what he really is" to be unworthy of conservatives. There are LOTS of legitimate reasons to critize the guy, not based on who his grandparents might have been.
Obviously not by anyone who has ever seen an actual Arab. Obama's father is jet black. But, finding crazy on the internet is kind of like finding wet in the ocean.