Because Arabs ARE a single subrace. Arab speakers are not. Muslims are not. Arabs are.
Now, genetically it appears that Arabs originated at the Ethiopian-Arabian Peninsula narrows between what is today Djibouti and Yemen, as an admixture between west asians (Anatolia-Levant-Iran today) and Africans.
During the Arab expansion (wars of conquest) that destroyed the ancient world’s great civilizations (Egyptian, North African, Levantine, Persian, Byzantine, and Roman), and led to the Abrahamic (jewish, christian, islamic) dark age, arabs interbred, particularly with slaves, because interbreeding of slaves was permitted.
So while Arabs INTERBRED with the civilizations they destroyed, and exploited for slavery, they remain a genetically and morphologically identifiable subrace.
West Asian Major Race
===West Asian (Iranian) Race
Iranian Race ( Armenian(R1b/J2) – Jewish(E1/J) – Greek(I2) — Southern Italians(I2) — Turk – Kurd – Iranian – Jordanian – Iraqi – Assyrian – Druze – Lebanese – Georgian – Caspian – Palestinian)
Tajik Race (Tajik – Bukhara Arab – Shugnan – Kallar – Sourashtran – Yadhava)
=== Arab (Semitic / Iranian-African?) Sub Race
(J) (Kuwait, and southern peninsula)
Kuwaiti Race* (Kuwaiti)
Arabian Race (Saudi – Yemeni – Bedouin)*
Egyptian Race (Egyptian)
=== North African Sub Race
North African Race (Moroccan – Libyan – Tunisian – Canarian)
Berber Race*** (Berber)
Algerian Race (Algerian)
We westerners ‘conflate’ Islam, Arab, and Arabic out of convenience and frankly inability to tell the difference (and lack of interest) – and rationally, because stereotypes are the most accurate system of measurement in the social sciences. Most of us still can’t tell east asians apart either. Yet we can tell which tribe or clan ethnic europeans come from.
CAN YOU TELL THE DIFFERENCE BETWEEN WHITES?
I mean, it’s hard for most, but I can tell high, middle, low german, celt, scandinavian, east baltic, polish-ukrainian, russian apart. It’s less easy to tell finno-hungarians, romanians, and southern slavic peoples. and it’s pretty easy to tell northern europeans (germanics) from southern europeans (with black hair), from sardianins, from greeks, from turks. Even if they’ve been intermarried over generations. Can you? Probably not.
So, you call us white, or western, but we differ substantially.
And if not, why would we not treat you likewise?
(I do science.)