the ideology of language hierarchy 諸言語の間にはヒエラルヒー（上下関係、階統秩序）があるという考え方
This is the sets of beliefs, norms and values that linguistic practices can be labeled and divided into different categories (like “language”, “dialect”, and “slang”), that there is a hierarchy between such categories ("languages are superior to dialects", for example) and that some languages have higher status than other languages.
(1) Visit this webpage - "What does a language hierarchy tell us?" - to become familiar with some ways of thinking and talking about "language hierarchy."
(2) Visit this webpage, watch the video, and read the transcript to think about different languages in your life and in society, and the different roles (and values) that they have. Which languages have a higher position? And which ones have a lower position - or a position somewhere in the middle? Why?
What is the language hierarchy that you imagine and have created?
How is it the same as or different from other people's language hierarchies?
What social/political purposes do linguistic hierarchies have?
(3) The Guardian (2008, May 23). First languages fear second place. Retrieved from https://www.theguardian.com/education/2008/may/23/tefl.gwladysfouche
(4) The Guardian (2018, May 22). Why speaking Spanish is becoming dangerous in America. Retrieved from https://www.theguardian.com/us-news/2018/may/22/speaking-spanish-dangerous-america-aaron-schlossberg-ice
(5) Office of the United Nations High Commissioner for Human Rights (OHCHR) (no date). Language rights of linguistic minorities. Retrieved from https://www.ohchr.org/EN/Issues/Minorities/SRMinorities/Pages/LanguageRights.aspx
(6) The British Academy (no date). The digital language divide: How does the language you speak shape your experience of the internet? Retrieved from http://labs.theguardian.com/digital-language-divide/
References
University of Groningen (no date). Multilingual practices. Retrieved from https://www.futurelearn.com/courses/multilingual-practices/0/steps/22638
University of Groningen (no date). What does a language hierarchy tell us? Retrieved from https://www.futurelearn.com/courses/multilingual-practices/0/steps/22639
Weber, J-J., & Horner, K. (2012). Introducing multilingualism: A social approach. London: Routledge.