Check out this article from Jihad Watch by Hugh Fitzgerald who answers the question saying
This has been dealt with by many ex-Muslims, including Ibn Warraq, who point out the obvious: 80% of the world's Muslims are not Arabs and do not know Arabic. Yet they are treated as Muslims, and believe themselves to be Muslims, and act upon what they read in Qur'an and Hadith. Are all of them grossly misinformed?
The article goes into much greater depth in answering the question.