I've been reading this thread with some interest but I have to chime in as the OP has...forgotten a lot of details about the setting he's calling racist. Not once has he mentioned the Ethengar or Atruaghin, the Mystaran equivalents of the Mongolians and Native Americans, and the fact that orcs in Mystara assimilate the cultures of the people they fight against the most. There's another clan of orcs in the Broken Lands that emulate the Roman legions, but apparently copying the Romans is fine. The Ethengar book is considered one of the best gazetteers in the line, while the Atruaghin book was notoriously rushed.
By removing the context behind the races you remove what made those orcs unique to the setting. The Red orcs dress and act that way because they fought for centuries against the Horse Clan before they were separated by an act of divine magic. But the Red orcs still copy the culture of the people that fought them to a standstill. The yellow orcs still fight the Ethengar, and believe by using their tactics and copying their customs they will gain a measure of their opponent's power. The black orcs dress in vaguely Thyatian gear, march in formation, and try to fight like the Legions that they witnessed crush all before them years ago. Orcs copy cultures in Mystara. The beastmen races were created by a jealous Immortal to throw down the kingdoms of men and demi-humans, and she did this by reincarnating the souls of the evilest mortals into a new race who over the years evolved into the various humanoid races.
The Aztec styled humanoids are a bit more complicated because they worship Atzanteotl, the patron of corruption and betrayal. He came from a culture similar to the Aztecs, and tries to corrupt other races into his worship. Every race he corrupts he has take up the culture of his original people. The Oinkmarians are just one of the groups he's corrupted. The schattenalfen, the original Azcan of the Hollow World, and the Tiger Clan of the Atruaghin also fell under his sway, and all have adopted Aztec trappings. Aztanteotl then tells his different followers that they are his true worshipers and to kill anybody who claims that they are his true followers. Meaning all the groups hate each other. He's a bit of a jerk.
The Piazza has a standing rule if you don't like something then give an example of how to change the lore to make it positive. The setting is rife with continuity problems. Thorfinn has spent years getting the errors in cartography right. It's an incredibly welcoming and friendly board as long as people obey the rules. The first rule is if something is problematic, give a suggestion on how to fix it. People have dumped near doctoral theses on that page explaining the problem and their suggestion on the solution and gotten equality long diatribes in response. It's often funny, and quite entertaining. But they take the whole of the setting into consideration, without cherry-picking.