Is there hard evidence that this is bad? Resource depletion is among the highest risks to civilization. Seems straightforward that severe population decline should be desired, and voluntary refraining from reproduction should be welcome. (Please don't just extrapolate the trend till extinction. See http://xkcd.com/605/ . )
It's bad because Japan has an extremely low net migration rate. For comparison Australia has 16x that of Japan. So whilst globally yes we should be aiming to reduce the total population Japan specifically has serious problems.
Oh, wait, you were speaking from the perspective of the corporations and rich investors who have to pay wages.
Funny how you adopted that perspective when you are a worker yourself.....