Why would it be silly in the United States? Charging women and men different amounts for an otherwise identical service is prima facie discriminatory.
As the
Civil Rights Cases made clear in 1875, there is no directly judicially actionable ability of the Federal government to intervene in private discrimination. The later Civil Rights Act of 1964 made use of Congress' Commerce Power. Hence in the US context, if Congress were to pass a law requiring the same price for men's and women's haircuts, it would be considered a valid use of the Commerce Clause, but absent such a law, a court or an administrative tribunal could not issue a ruling such as the one the Danish Board of Equal Treatment issued.
