Workaholism -> backfires and is bad for the economy
and in recent threads here on HN:
Workplace surveillance -> backfires, people feel controlled and performance suffers
Government espionage in USA -> backfires, people lose trust in US businesses
I don't feel that this is the strongest argument. "Please treat us better, it is in your own interest!"?
Germany's vacation was achieved through politics (labor laws) and unions (labor contracts).
The economic argument probably won't work, since economic considerations (real or imagined/short-term/local maximum...) have led to the current situation in the first place.