"The true Arabs are the people of northern Arabia, the Nefud, and the arid portions of Syria, Jordan and Iraq (the Byzantine Emperor Leo who repelled the Umayyad assault on Constantinople was of Arab descent, of the Ghassanid line of Syria). All other "Arabs" are Arabicized peoples, whether that be closely related ones such as the people of Yemen (Sabaeans) or the Levant (Armaeans), or more distant peoples such as Egyptians (Copts) or Maghrebis (Berbers)."
Notice that Kurds, Palestinians/Philistines, and Jews do not fit into the above definition of what constitutes an Arab.
Turns out they aren't Arabs even if they speak Arabic. This is particularly so when it comes to the very Arabicized Levantine people who today are known as Lebanese and who were in ancient times also known as Phoenicians and Caananites.
The Isaac/Ishmael dichotomy is another way to look at the fundamental differences between the Arabs and the Jews, but it's when we get to Sarah and Hagar that the full difference is expressed. Hagar is clearly ethnically, politically, socially, and culturally different from Sarah.
Those who take the Bible literally really don't have to go much beyond that to figure out the differences in the two groups. Those who view the Bible less literally might imagine the early rabbis who "edited" the ancient texts piecing this together because it made a lot of sense for the Hebrew and Aramaic speakers of the Mediterranean coast to have different origins than the Arabic speaking folks from the desert.
Either way, the differentiation is truly of Biblical proportions. However, the modern scientific evidence is telling us that the Palestinians are part of the Jewish/Levantine milieu and not that of the Arabs.
"Palestinian" Arabs are indistinguishable from "Egyptian" "Jordanian" "Saudi Arabian" "Kuwaiti" and "Iraqi" Arabs because all these titles are 20th century political constructs.
The Arabs who call themselves "Palestinians" have nothing to do with the ancient Philistines or Phoenicians.