Most people don’t realize that this is a family quarrel. It goes all the way back to Jacob and Esau, brothers. Begin at Genesis Chapter 25.
This argument has continued since then.
At what point in history did “Arab” emerge as a cultural/ethnic idenity?
I think it goes even further back than that. Abraham had two sons, Issac and Ishmael, by his wife Sarai and her Egyptian handmaiden Hagar. Sarai later had Hagar and Ishmael expelled.
Gen 16:5 And Sarai said unto Abram, My wrong be upon thee: I have given my maid into thy bosom; and when she saw that she had conceived, I was despised in her eyes: the LORD judge between me and thee.
Speaking of Ishmael, the forerunner of the Arabs:
Gen 16:12 And he will be a wild man; his hand will be against every man, and every man's hand against him; and he shall dwell in the presence of all his brethren.