How has Islam divided Egyptians?

Answer 1

Islam, per se, has not divided Egypt, save for the fact that some Egyptians are Muslims and some are not. However, Islamism has dealt a huge blow to Egyptian unity. (Islamism is the idea that Islamic Law should be enforced as the official law of the land in a country.)

When Egypt was viciously yanked into the modern world through the creation of the English protectorate, the population was majority Muslim and the leaders had been Middle Age-type Islamic theocrats. However, modernity gave rise to two major political themes in Egypt.

The first was Arab Socialism and Pharaonism, which sought to create states based on Arab Unity, Arab Values, and Egypt's historic grandeur. Although many of these values come from Islam, their legitimacy now came from Arabs holding to those values rather than Islam having provided them. Since the unity also tracked to Egypt as a national construct, the Coptic Christians and (at the time) Egyptian Jews were engaged as part of Egypt. A number of Copts were very prominent in the Arab Socialist movement and the Pharaonic movement, since these movements were inclusive of Egypt's diversity.

The other was the Islamist movement which saw only Islamic Values and Islamic Law is being the rightful government and held that a true merger between Islamic Jurists and the Government could rule morally and properly. This motivated the Muslim Brotherhood in Egypt. Under Islamism, it was necessarily the case that Non-Muslims, like the Coptic Christians and Jews would be second-class citizens, subject to unfair and prejudicial laws. Under the year-long presidency of Mohamed Morsi, Egypt's only Islamist President, Christians were shot to death inside of churches, more churches were destroyed, defaced, or smashed than in the previous decade, and the President made messages equating Jews to apes and pigs.

Both of these philosophies remain relatively popular in Egypt today, although the repression from his successor, General Abdel Fattah el-Sisi, has resulted in pure secular authoritarianism. This is closer to Pharaonism, but lacks the fundamental feeling of cultural unity and expressiveness.

Answer 2

Islam does not divide, rather it unites. It is the vested interests of the people which divide nations and societies.