A 2010 proposal to switch some programming on Guangzhou television from Cantonese to Mandarin was abandoned following massive public protests, the largest since the Tiananmen Square protests of 1989. - Wikipedia
I did not know about the 2010 event until now.
Cantonese is a language. The fact that it is often referred to and demoted to a dialect probably has to do with its lack of a formal written format.