Jack Vance was politically far-right, he was a racist and non-apologetic about it: Non- "white" people were not fully human to him and his works reflect this. All his alien species are basically just racist stereotypes, simplifications of Earthly ethnic groups and cultures through his own racist vision.

This is even now not uncommon among US of A authors of fantastic fiction; to them "Americans" = "Humans", non-"Americans" = "Aliens" is pretty much standard fare, any other country like an alien planet which they are incapable of comprehending but as a distorted, stereotypical simplification while their own "all-American" characters are "universal humanity" to them. Even those authors claimed as "progressive" or "left-wing" in US of A terms (meaning a bit more moderate members of the right-wing) tend to share this, including the few coming from among the minorities.

There's no reason to sugar coat this or find excuses for it, anymore than to racism in the works of authors like Philip Roth among the mainstream USA literature. Its just what he was and what his work has saved of his person and worldview. Either you accept this as part of Vance's character and work without accepting his "values" or you move past him and read something else.

But then you pretty much has to move past the everything written in the United States of central north-America, because under almost of their literature lies this racism that is bred and kept up by their inability to understand the world, of anything different from the "American" existence as spoon-fed to them from the womb on-wards.

A chasm separates them from humanity.