Many anti-racist activists would still have to swallow for a moment when their daughter came home with a black guy. Our gut reactions are not always congruent with our rational beliefs. There is a famous psychological test that measures these implicit associations.
Racists are well aware of these phenomena. Those "birthers" who keep questioning whether Obama was really born in the US and those people who keep complaining about Obama's friends among black radicals have one main goal: raising your awareness that Obama is black and by that calling on the prejudices that many of us have about black people.
In Syria we see the same. The blacks of Syria are the Alawites who for centuries were heavily discriminated because some claimed that they were no true Muslims. Syria's rebels have their best to raise everyone's awareness that Assad is an Alawite and that there quite a few Alawites in his close circle. All those flimsy complaints about discrimination by the Assad government of non-Alawites have this goal. This explains also the success of preachers like Arour who found their own way to highlight that Assad is an Alawite.
It always amazes me how easily the Western press copies such propaganda without being aware of its ultimate goal. It reminds me of all those articles that we saw about the gap between Roman and Byzantine culture that we saw at the eve of the Yugoslav wars. It came straight from Croat propaganda but few journalists seemed aware what they were doing when they copied it.