Although I don't think the 'not wanting to be self-identified with English' is a valid reason, the fact that you can't really verify competency levels is a very good reason not to include this in a map. I know a lot of people who took several years of a foreign language in the U.S. in high school but cannot speak them.  As long as it's mentioned in the article about the wide-spread use of English, I don't think it needs to be on a map.  I doubt there is a consistent way to determine competency levels of English around the world.