Hey Music and all,
I guess, sometimes it's funny, and sometimes it's not. Depends on many factors: the joke in question, the people, the context, how it's told etc. To my mind, if any one of those conditions isn't right, then a joke can go turn offensive.
Sometime, when I been insulted by a joke, I try to be sober about it, and tell people why it's not funny. For instance, the X Street joke... I would have been okay with it, but not too impressed. But if someone then said "yeah, it's funny because it's true" or some such, I'd point out that MF rape happens too (and more often, so I believe) but that's certainly not a matter for comedy... so why is it okay when it's guys involved? Would someone make a comparable joke about miniskirts and dark alleys? No - it would be unacceptable.
See, my problem with the X Street joke kicks in when someone ties it back to reality.
But, things to take into account: people often tell jokes when they're uncomfortable, so avoid lashing out, and try not to get offended. Also, some bad jokes are hilarious, but only when told by the right people (for instance... the aristocrats

) and sometimes - through no fault or bad intention - someone can accidentally make a good joke bad just because they lack timing or the comedic flair. I think we've all done that... made a gag that was in poor taste. I have, and regreted it.
Racism gets me too, like that; to my discredit I have not always stood up against it, or walked away from the person making the comment, jibes or cracks. I've actually been thinking about that a lot today... it usually slips by me when someone says "I'm not racist/homophobic/sexist, but... [and then launches into a slur]". It's hard to call them out, and say, "actually, you are racist/phobe/sexist".
I'm going to watch out for that. Not being a moral policeman or anything; just comments like that bother me, usually afterwards.