I don't find these situations humorous. At all. They are cases of amputation, mutilation and grievous bodily harm. This is physical abuse, and a heinous form of torture that I do not abide.
To some degree I get why people find it funny. On family shows, like America's Funniest Home Videos, half the clips seem to be of guy after guy somehow injuring his groin - whether it be from an errant football, a miscalculated skateboarding trick, or an overly enthusiastic dog. When you see these scenes played ad nauseum against a laugh-track, it's hard not to find yourself conditioned to accept that as harmless entertainment.
I also see a lot of people making the assumption that the victim had perpetrated rape and this is likely their just-desserts. In this most recent story, there is no real information on who the attacker is or their relation to the victim. All assumptions are based on "Man's penis attacked, therefore man must have done something to deserve it." I don't think I need to state all the ways that's fucked up. Having a penis does not make one a rapist, and having one's penis mutilated does not make one a rapist.
Let's say that there is a statistically large portion of these men who are guilty of having committed rape. I still do not support genital mutilation, in the same way I do not approve of rape or torture as a punishment. Not only from a pacifist point of view, but also because I feel encouraging this kind of revengeful violence does more harm to those "righteous" folks who carry it out and open the door to these kinds of acts being committed under an increasingly broad set of conditions, just as corrective rape is presently used.
Yes, yes, I know. I'm a real buzzkill. Gosh, if you can't joke about rape in front of me, and now I'm harshing on puns about genital mutilation, what is there left to joke about?
How about knock, knock jokes?
I honestly don't give a crap what you have left to joke about, rape and genital mutilation aren't funny.