"the desire by a group of people who share the same race, culture, language, etc. to form an independent country Scottish nationalism"
Emphasis on the "share the same race, culture, language, etc".
That's very different from the simple notion that nations should exist.
At the root of this are feelings of superiority to those that don't share those aspects -- the out-group -- as illustrated again and again and again by the oppression of the out-group by the in-group.
"Obviously anyone would denounce xenophobia, racism, bigotry, and fascism and all the other vile actions you mention."
Obviously not anyone, or they would not be so popular.