Encyclopedias are a good place to start in order to get background info, brainstorm, and find topic ideas related to language diversity, language justice, antiracist writing practices, and/or inclusive writing practices.
You are focusing on two areas. The first area focuses on finding viewpoint sources such as opinion articles/editorials and pieces of visual rhetoric (cartoons, ads, bumper stickers, t-shirts, etc.) related to these topics.
You will find this type of information in popular magazines and newspapers as well as social media/blogs/vlogs/websites. Scholarly journals also have editorial pages in which writers express an opinion. Look for the editorial column when you search inside the journal.
The second area focuses on finding informative sources regarding the larger historical, political, and cultural contexts on these topics. The scholarly journals are good sources for this type of research. There are scholarly books you can find on this topic by searching the RIT Libraries Catalog below.