Actually, the more literate the person is, the easier it would be to convince him -- so long as it's literacy in the Qur'an and Hadith. And the black flag is the least of the prophecies. There are hundreds of "Signs of Qiyamah," and it isn't hard for the mullahs to make the case, Hal-Lindsey-like, that they are coming to pass. And these prophecies guarantee them victory over an Infidel Superpower, so don't expect a few stealth bombers and daisy cutters to make them change their minds.
Personally, when I hear "Black Flag" I think of that brand of bug spray (which if you lived in south Florida you would know what I'm talking about), and I would like to use some bug spray on these al-Qaedic bugs.
An interesting factoid is that people who wear black turbans are entitled to do so because they are "descendants of the Prophet Mohammed". Now, considering that
the false-prophet Mohammed had 11 wives at any given time (and I have seen a list of 23 women he was married to in toto) inluding the little 6-year-old girl Alyesha;
AND that he owned 28 slaves, 17 of whom were women;
AND that he also probably had a number of concubines;
AND that he was not above raping other women and was well-known for his energy;
..... I am surprised that we don't see all 1,000,000,000 Muslims wearing black turbans.