A case in point: In 1923, the U.S. Supreme Court invalidated a women-only minimum wage law. The Court noted that the law infringed on liberty of contract, and therefore was presumptively unconstitutional.
Justice George Sutherland, writing for the Court, proceeded to distinguish the case at bar from previous decisions upholding women-only maximum hours laws:
In the Muller case, the validity of an Oregon statute, forbidding the employment of any female in certain industries more than ten hours during anyone day was upheld. The decision proceeded upon the theory that the difference between the sexes may justify a different rule respecting hours of labor in the case of women than in the case of men. It is pointed out that these consist in differences of physical structure, especially in respect of the maternal functions, and also in the fact that, historically, woman has always been dependent upon man, who has established his control by superior physical strength. The cases of Riley, Miller, and Bosley follow in this respect the Muller case. But the ancient inequality of the sexes, otherwise than physical, as suggested in the Muller case (p. 421) has continued "with diminishing intensity." In view of the great -- not to say revolutionary -- changes which have taken place since that utterance, in the contractual, political and civil status of women, culminating in the Nineteenth Amendment, it is not unreasonable to say that these differences have now come almost, if not quite, to the vanishing point. In this aspect of the matter, while the physical differences must be recognized in appropriate cases, and legislation fixing hours or conditions of work may properly take them into account, we cannot accept the doctrine that women of mature age, sui juris, require or may be subjected to restrictions upon their liberty of contract which could not lawfully be imposed in the case of men under similar circumstances. To do so would be to ignore all the implications to be drawn from the present day trend of legislation, as well as that of common thought and usage, by which woman is accorded emancipation from the old doctrine that she must be given special protection or be subjected to special restraint in her contractual and civil relationships.This is the most equalitarian rhetoric one will find in a Supreme Court about with regard to women for almost fifty years. Yet historians, even feminist historians hostile to protective laws for women, give Sutherland no credit. Various historians have accused Sutherland of “male bias and corporate favoritism,” of being “disingenuous,” of making “a farce of women’s equality,” and so on. In short, perhaps relying on Sutherland’s reputation as a “conservative,” historians have simply assumed that Sutherland was insincere.
Yet, it wouldn’t have taken any of these historians much effort to discover that Sutherland was a longstanding women’s rights advocate. He introduced the Nineteenth Amendment into the Senate when he was a Senator for Utah, campaigned for the passage of that amendment, helped draft the Equal Rights Amendment, and was a friend and adviser of Alice Paul of the National Woman’s Party.
One obvious lesson from all this is not to anachronistically assign ideological positions to people based on current ideological alignments. Sutherland may have been “conservative” on economic issues, but in 1923 there was no strong correlation between one’s views on women’s rights (or civil rights and civil liberties more generally) and one’s views on economic policy. Indeed, mainstream views in Progressive legal circles regarding women's "place" would be considered downright reactionary these days.
But there is also a broader issue of making conclusory statements about a historical figure without actually doing any research about that figure. Sutherland’s views on sex equality were not the focus of any of the erring historians’ work, but if they were not going to bother looking into those views, why raise the issue to begin with?
For those interested in the topic of protective laws for women and the law, I devote a chapter of Rehabilitating Lochner to it.