Yes, Paul Krugman is right to be scared about China's economy because adjustments must e made quickly to avoid a complete and severe downturn. For decades, the country enjoyed growth
and now it is becoming a tough challenge at a very slow pace. Transition can lead to a nasty recession.
China has been experiencing major economic growth for a long time now. This kind of growth is hard to maintain with. GDP in the country has been decreasing over the years which may lead to a recession. This is enough reason to make the economist Paul Krugman worried about China's economy.
The Chinese economy has to make the transition from a consumption driven economy to one of investment but they have many assets in their favor. The country has a strong sense of nationalism and a history that proves the Chinese people are resilient, so this change may cause a recession but it won't last long. They just need to start making this transition now.
Unless we lived in China, or Paul Krugman for that matter, it is idiotic to fear their economy at this time. There are far worse things to fear. One of such is the United States economy. We are living in a moment of false good. Just because gas prices are low, doesn't mean our economy is any better.