Consider the following excerpt from Stefan Zweig written in the early twentieth century: "This 'social morality,' which on the one hand privately pre-supposed the existence of sexuality and its natural course, but on the other would not recognize it openly at any price, was doubly deceitful. While it winked one eye at a young man and even encouraged him with the other 'to sow his wild oats,' as the kindly language of the home put it, in the case of a woman it studiously shut both eyes and acted as if it were blind." What does Zweig argue about the double standard that existed in the early twentieth century?