I could post other images of horses and warriors before the stirrup, but the Tapestry is a familiar source.

Alexander was strictly Greek. Macedonian royalty was even allowed to participate in the Olympic games, a competition ritually banned to non-Greeks. The Macedonian people were considered non-Greek by the Hellenes because they seemed primitive.

Like all satire, it plays on an intentional (one hopes) misunderstanding of the object of the satire.