despite Gary Gygax's abuse of English language, orcs are not a race.
Gygax’s use of the word "race" to refer to non-human entities like elves, dwarves, and orcs probably derives from his sources.
Appendix N
The Hobbit, JRR Tolkien:
"Ever since the fall of the Great Goblin of the Misty Mountains the hatred of their race for the dwarves had been rekindled to fury."
The Lord of the Rings, JRR Tolkien:
"No dwarf could be unmoved by such loveliness. None of Durin’s race would mine those caves for stones or ore, not if diamonds and gold could be got there."
"Suddenly the slow-kindled courage of his [Merry’s] race awoke."
"In the last years of Denethor I the race of uruks, black orcs of great strength, first appeared out of Mordor"
"These creatures [orcs], being filled with malice, hating even their own kind, quickly developed as many barbarous dialects as there were groups or settlements of their race"
In Appendix F, ents, orcs, trolls, and dwarves appear under the heading "Of Other Races".
Three Hearts and Three Lions, Poul Anderson:
"Curiously, for beings said to be soulless, the Faerie race were under severe physical handicaps, and must rely mainly on guile."
The King of Elfland’s Daughter, Lord Dunsany:
"A curiosity arose in the forest amongst that brown mass of trolls, for their race is profoundly inquisitive."
Land of Unreason, L Sprague de Camp and Fletcher Pratt:
"These kobolds are a race that consort not with us, loving labor like Egyptians."
Tolkien's Sources
These use the word "race" in a similar way.
The Princess and the Goblin, George MacDonald:
"In these subterranean caverns lived a strange race of beings, called by some gnomes, by some kobolds, by some goblins."
The Marvellous Land of Snergs, E A Wyke-Smith:
"The Snergs are a race of people only slightly taller than the average table but broad in the shoulders and of great strength. Probably they are some offshoot of the pixies who once inhabited the hills and forests of England"