Man, this is such a fucking confusing case.
I don't want to support harassment in a professional context, but I find it really hard to think of what those guys did as harassment.
I want to live in a world where you can make crude jokes with your work friends and not be afraid about who is listening in. Harassment shouldn't be defined by a list of taboo subjects or stupid rules. Harassment should mean intentional actions that make someone feel uncomfortable or afraid. That means there needs to be some reasonable leeway made for situations where you don't know you're making someone uncomfortable. It makes sense that we should be careful about the kind of jokes we make directly to people but we shouldn't by default have to assume that someone with absolutely zero sense of humour is listening in.
People should be free to make jokes and flirt and do whatever they like at the work place, as long as no-one minds. We have to spend half our life at work, what's the fucking point of having to be a robot the whole time?
Sexual jokes aren't necessarily sexist, nor are they necessarily harassing. Neither is flirting, or kissing or flat out having sex, for that matter. (Might be inappropriate for a work environment, but doesn't have to be sexual harassment, does it?) On the other hand, if you do it in an inappropriate way, looking at someone could be genuinely terrifying harassment. I bet if you were careful and sadistic enough, you could turn any innocuous interaction into something that, over time, makes someone feel deeply uncomfortable.
Imagine if we work together. Imagine I am perfectly normal with everyone else, but when I put my reports on your desk, I slide them on gently, looking you in the eye, then I just hold them there, palm flat on the desk and I smile. I let the smile last just a second too long, then I go off and carry on being relatively normal with everyone else. I do that every single day, and each time you look less and less comfortable, and each time I either don't react or seem to enjoy your discomfort. How long would it take before that became very unpleasant for you? What kind of possible rule structure could be in place that could conceivable prevent me from doing this without requiring some communication from you? What would you ban? Looking someone in the eye and smiling for too long? How many seconds is too long? How would you time it?
Moreover, how the fuck would this rule structure be able to distinguish intentional harassment from the situation where it turns out I am slightly autistic and I happen to really enjoy looking over your shoulder at your screensaver when I drop my reports on your desk?
We have to set the rules at a place of compromise and rely on explicit communication to sort everything else out. Otherwise we'll end up with segregated offices or women in fucking Burkhas or some other retarded solution to the general problem of otherwise clever people being unable to cope with social interaction.