Page "Names given to the Spanish language" Paragraph 26

For some, this use of the term castellano is a political or cultural statement that Spanish is only the language of Castile and perhaps some areas that Castile colonised, but not the language of their region, where they consider the only legitimate language to be the regional one, i. e. Catalan, Basque, Galician, etc.

This stance is common in regionalist circles.