Because of the discussions during the last couple of weeks, I've learned a lot about Title VII protections for the workplace. I wish we would look towards Title VII for guidance, because many of these nuances have been fleshed out by case law and the EEOC.
The courts (in my novice understanding) only look towards behavior which is discriminatory, and there's a set of guidelines to consider. A discussion about apps and websites for sexual health aren't discriminatory towards a protected class of people, even if there are jokes involved. This is how family planning center can have conversations about birth control while also being under Title VII law. There are also some "bona fide occupational qualification" exceptions, like not needing to use men as a Playboy Bunny.
Sexist imagery would fall under sexual harassment because it “may be found to create an atmosphere in which women are viewed as men’s sexual playthings rather than as their equal coworkers”, quoting from Barbetta v. Chemlawn Services Corp. A defense that an organization can do, to say that it is not discriminatory, is to prevent sexist imagery from being displayed.
However, sexual imagery which does not portray coworkers as unequal wouldn't count. This would of course depend on the larger context. Covering a wall with pictures of anatomically correct genitalia, and with no work meaning, is of course different than using pictures of genitalia to show how an STD progresses while at a medical conference. The courts say there isn't a single guideline but rather a "constellation" of factors. Still, they say that it's usually not that hard to figure out.
However, this code of conduct doesn't look towards the previous history in order to explain itself. Even the phrase "code of conduct" is different than Title VII, which is an anti-discrimination policy and explicitly not a code of civility.
I've been thinking about the difference this way: two people can have a conversation which is uncivil but calm; perhaps talking about each others' atrocious coding practices, or deriding the bad leadership practices of their shared company. These can be impolite, but not unwanted by the two participants. In that case, I don't think there should be cause for a third-party who overhears the conversation to intervene and say that they aren't being nice, either to each other or to their non-present boss. While an anti-discrimination statement gives that right to third-party people, should there be racist, sexist, or other discriminatory action or speech.