Christianity created white European identity during the Middle Ages. This first unity was described as Christendom, and it led to the development of a distinct Western Civilization. Attempts to unite white people outside of Christianity is rebellion against our historical identity. This is not to reduce the reality of European genetic similarity, but to recognize the force that drew the boundaries our group historically policed.

A liberal discussed this in 2011 while in the process of condemning euro-centrism. Of course, I don't endorse his worldview, but I think he makes a good point (please ignore his liberal virtue-signalling language):
"During the Middle Ages, the Western European started to develop a certain sense of superiority. In these times the main difference between ‘Europe’ and ‘the rest’ was based on religion. The Western Europeans claimed that they, and they alone, were the bearers of the ‘true’ religion, were the only ‘true’ believers in the holy Christ. I do have to add that a common religion was virtually the only thing that bound the Europeans: for the rest the political and cultural differences couldn’t be greater. Europe was nowhere near a unity."
The author goes on to write about how historical Greek philosophy didn't enter the West until the Renaissance era around 1453. European Civilization was built on Christianity before later being influenced by ancient philosophical thought. Christianity is the foundational core of our identity.