When it comes to unprofessional language in commercial, scientific, and engineering endeavours, there seems to be two assumptions people make:
1. All women are offended by the sorts of words and phrases used by 9th graders in their daily speech.
2. No men are offended by the same sort of language.
Both assumptions are incorrect.
Now, in most situations, I think that people should be able to say what they want. You can talk about body parts in naughty ways, and you can say all manner of insulting things (right or wrong) about anybody's religion. Basically, anything short of threatening to kill people. And if people get offended, they can shove it. I think that the proper and polite thing to do is to make sure that someone who doesn't want to hear what you say isn't forced to listen -- that to read what you wrote or hear what you said requires some positive action on their part, so if they don't like it, it's their fault for seeking it out.
However, in a professional setting, it's time to act like an adult. Discussions of sex and insults about religions are out of place, not because they're *fundamentally* inappropriate, but because they're accepted as inappropriate for professional and public settings. I'm sorry. I don't care how much you and your pals get a kick out of jokes about Jews and dead babies, people shouldn't have to listen to it at the office.
So, then there's this ambiguous situation with FOSS projects. Is this play time or work time? It's kinda both. People do it for fun, but if you don't want to make it a public thing, then you don't put it up on github. If your objective is to get public participation in a technically-oriented project, unprofessional language is out of place. If you want people to take FOSS in general serious, then unprofessional language is out of place. Linus Torvalds didn't publish the source code to Linux because he thought it would be hillarious or an asshole thing to do. The purpose was to attract people into a development community around the project.
In general, I object to certain subject being out in public where it's shoved up everyone's noses. Nude beach? No problem, because you have to travel there to see it. Nude parade down my street? That depends on the purpose, but there are many ways in which human nudity can be a good thing, for artistic, educational, or scientific purposes. (In general, I wouldn't be offended unless it was just really tasteless.) What about people in the nude parade having sex while they travel on floats down my street? No fucking way. I'm not a huge fan of Islam, and I think that its adherents deserve a great deal of criticism, constructive and otherwise. On the other hand, I would find it unacceptable to have to a parade whose purpose was to shout anti-Islamic hate language for everyone to hear. Speaking of screwing in the streets, that's one of the things that bothers me about gay pride parades. Standing up against oppression from bigots who hate you for a perfectly natural thing is good (homosexuality is ubiquitous in the animal kingdom). However, this does not require that your presentation be so hypersexualized that I can't take my kids to see it. (Honestly, we just dont need sex in the streets. Gay people are as normal and weird as any other subset of the population, living their lives, working jobs, etc. Connecting "gay" with "hypersexual" in a public event gives people the wrong idea.)
The bottom line is that people need to learn to be considerate and have some professional decorum. If you're going to do or say something that might insult someone, do it in a principled way as a means to be constructive. Do it because you DO give a shit, not because you don't. This applies to FOSS projects as much as to any other situation.
Although I wouldn't necessarily say you have the "right" to be an asshole, it's vital that you have that freedom. Consider obscenity laws that restrict porn to certain venues. Those may or may not have some value, but laws that try to curtail it entirely are undoubtedly bad. Why? They would be part of the slippery slope of eroding out freedoms in other areas. Indeed, it is critically important to the health of our society that some people act in assholish ways, because it helps us to not get stuck with one defintion or another of what is acceptable. 60 years ago, it was unacceptable for a "negro" to sit at the front of a bus. However, we should all be grateful that Rosa Parks took the risk she did, because it played a role in a much needed overhaul of America's concepts of civil rights and fundamental human equality. In other words, you never know what "asshole move" might lead to a change for the better in society, rather than just being some random crap out of someone who never left junior high school. But at the same time, keep in mind that what Rosa Parks did wasn't meant to insult people, per se -- it was a deliberate and principled act against oppression. There's a stark contrast between that versus random potty talk on github that may play an insignificant role in some day allowing the word "fuck" to be said on broadcast TV.