I think there’s a lot of truth to this. Partly maligning Sanger because of her association with Planned Parenthood. But more broadly using the unpleasant aspects of her to malign the left by association. The argument essentially is “Sanger was a leftist. And Sanger was a bigot. Therefore the left supports bigotry.”
Are you going to blame the large number of Republican senators who felt strongly enough about it to cosponsor the damned thing as well? Hell, even Strom Thurmond, Howard Baker and Ted Stevens were sponsors.