Some critics of this emphasis maintain that it denigrates regional and other varieties, and promotes the langauge of a dominant group, predominantly the educated middle classes, at the expense of others. However, the need for SE, in my opinion, is that it creates a central core of readily understood English, which facilitates communication and allows speakers to be more flexible and better equipped to particpate in a wider economic life.
I do get tired of some of the pettier obsessions, like regarding 'alright' as a dreadful mistake, but believe that people who can communicate with anyone in the widest speech community, and SE extends their range into the international arena, are better-off.
Does someone who speaks a strong NSE have an equal chance in the marketplace? I don't think so, and don't think that saying 'well, they should' is very helpful. In purely pragmatic terms, SE makes sense. That doesn't mean that there should be no tolerance of variation- I think there should, but sending someone out into the harsh realities of the job market with a reduced chance of fulfilling their potential strikes me as a waste of human resources.