Not all Christian Arabs are like that. The ones living with Muslim in the West Bank and in the Gaza strip are one and united for the common Arab palestinian cause.
Some of the most prominent members of the early PLO movement were Christian Arabs.
The funny thing is that it was the Christian Arabs who were the backbone behind Arab nationalism when they were under Ottoman rule. Christian Arabs believed that Pan-Arabism would work in their favour but they didn't realise that Muslim Arabs believe that Islam is an essential part of Arab nationalism as that is what brought them to their greatest prominence.
A famous Christian Arab who was one of the fathers of Ba'athism, Michel Aflaq had this to say about Islam:
What Aflaq saw in Islam was a revolutionary movement. In contrast to other nationalities, the Arab awakening and expansion was attributed to a religious message. Because of this, Aflaq believed that the Arab's spirituality was directly linked to Islam, therefore, one could never take Islam out of the equation of what is essentially, and essentially is not, Arab. Arab nationalism, just as Islam had been during the lifetime of Muhammad, was a spiritual revolutionary movement, leading the Arabs towards a new renaissance: Arab nationalism was the second revolution to appear in the Arab world. All Arab religious communities should, according to Aflaq, respect and worship the spirituality of Islam, even if they did not worship Islam in a religious sense – Aflaq was a Christian who worshipped Islam. Aflaq did not believe it was necessary to worship Muhammad, but believed that all Arabs should strive to emulate Muhammad. In the words of Aflaq himself, Arabs "belong to the nation that gave birth to a Muhammad; or rather, because this Arab individual is a member of the community which Muhammad put all his efforts into creating […] Muhammad was all the Arabs; let us today make all the Arabs Muhammad." The Muslim of Muhammad's days were, according to Aflaq, synonymous with Arabs – the Arabs were the only ones to preach the message of Islam during Muhammad's lifetime. In contrast to Jesus, who was a religious leader, but not a political leader, Muhammad was both – the first leader of Islam and of the Arab world. Therefore, secularisation could not take the same shape in the Arab world as it did in the West.
There are claims that he converted to Islam before he died.
You can't take Islam out of Arab nationalism and that's what Arab Christians realised.
@Apollo @CaliTedesse @Armadillo