You use of the phrase "pre-Islamic pagans" sounds like a slur.
Justinian did his utmost to crush the Neoplatonic Academies left in Greece, effectively strangling Hellenism out of the old Empire and setting Europe on course towards the Dark Ages. Were there really all that many educated "Arab" Pagans left anywhere to be snuffed out by the rise of radial Islamic Christianity in the 800s?
Then your premise has been justified, whichever way you look at it:
This is interesting.
Islam is over a thousands of years old. It is entrenched deeply into "Arab culture" - like the Bruka and child marriage. So should you stick to it? I think not and most educated Arab atheists will agree
Arab paganism was exemplified by female infanticide, which incidentally was also a hallmark of Hellenic paganism and is a continuing problem in societies where monotheism is not the major religion e.g. India. Incidentally, the strongest proponents of reform and women's rights in India were/are members of the Arya Samaj and Brahmo Samaj - both monotheistic schools of thought, the latter with strong influences from Islam. Islam, in fact, is the only religion where the daughter is not "given away" in a marriage ceremony by some male relative - and if we were to look at modern times, the spectacular failure of countries like the USSR and China to embrace a humanistic culture in the absence of religion and in fact a failure of the state to survive as such without reverting to religion is evidence that atheism is very much a failed philosophy with no practical advantage. The rise of atheism in India came long before Muslims travelled to India as traders, Indians developed the atheist school of thought in the Mauryan times:
Available evidence suggests that Cārvāka philosophy was set out in the Barhaspatya sutras, probably in Mauryan times. Neither this text nor any other original text of the Cārvāka school of philosophy has been preserved. Its principal works are known only from fragments cited by its Hindu and Buddhist opponents. Cārvāka philosophy appears to have died out some time in the 15th century.
And yeah, it failed. In a country where we still recite ancient Mantras of the first people to step into India out of Africa and have 60 million people attend the Kumbh mela going on since mythical times, we retain only fragments of the atheist school of the Carvakas. I remember reading somewhere that any school of thought anywhere in the world will find an analogy in India and this is true. We are not a replacement culture. We don't force people to dress like this or talk like that or shake hands if they don't want to - in general, we are a culture that tolerates a lot more diversity of thought than I have seen anywhere else in the world. We are a culture where everything can survive and if it doesn't survive in India, its not going to work out anywhere else either.
Outside of your classic religious denigration, and justifications for violence, even if just pretend, I seriously doubt there is much, if any, evidence of widespread "Arab" atheism.
I've actually been in touch with mulhids but for some reason after some time they lose interest in their own beliefs [see here:http://towelianism.wordpress.com/]. So I think there may be many Arab athiests but so what? It doesn't provide them a framework for life - all they have is the belief that they reject God. And then what? What next? Maybe like the Russians they can do drugs or alcohol and decide that nothing is worth it anyway. Or draw a few obscene cartoons which do no one any good and create more division and stress. Then what? Beyond the denigration of religion and religious people, what does atheism provide? Materialism can only satisfy people so far and a soulless existence is not a fulfilled one.