Real-life fashion police crack down on public pajama-wearers in China

Shanghai will host the World Expo next year, and city officials are preparing for the influx of foreigners with a campaign to ban citizens from wearing their pajamas out in the streets.
An article in the Chengdu Business Daily expresses outrage over the campaign as a civil rights abuse.

Excerpt:

Many Shanghai residents are used to loitering around the streets in their pajamas. But now the municipal government is making every effort to stop them from doing so, because it would be a "loss of face" for city authorities if a foreigner sees people walking the streets in pajamas during the 2010 World Expo. (...)

As a modern international metropolis, Shanghai has been playing host to foreigners for decades. So why have pajamas become embarrassing only now? And will it be okay for people to walk the streets in pajamas after the World Expo? Why should we change our habits and customs to suit foreigners' taste when we travel abroad as well as when we play host to them? Do we suffer from a sense of inferiority?

What's wrong with a person in pajamas?