Disney most certainly could require some kind of modest dress code - if the “buttless chaps” story is really true, this would put a damper on it. Also, prohibiting certain behavior would dissuade disgusting displays. After all, I believe public sex is illegal everywhere (well, maybe not in San Fransicko.)
It is true. My son saw it and pointed out the guy to his supervisor (lesbian. . .sort of. . .more on that below*). The supervisor said to let it go, not to make an issue of it, not to contact security. So, yes, they do have a dress code, rigorously imposed except for homosexuals. Public sex acts are also illegal on the park, but for homosexuals, they treat Disney World like, well, a Disney World of their own.
*The “lesbian” supervisor was married to a man for about 5 years when she decided she was lesbian. She moved out and in with a lesbian. When the supervisor decided she was not lesbian and tried to leave, she was assaulted by her “lover” and the lovers lesbian friends. The supervisor was tied up and nearly beaten to death. Her face is now chewed meat, according to my son.