Sure, this title sounds pretty offensive, but hey: maiming rapists sounds like my cup of tea, to be honest. Haven't even seen the movie, but absolutely this could be funny! I guess that punishing people isn't normally a funny thing, but I think we could definitely make an exception here.
For those who haven't seen the extended uncut version (available on DVD and bluray). The rapist getting his manhood shot off is not the only one. A group of guys getting out trying to rape women getting their manhood shot off. It's so funny because of that. I was laughing when I first saw it. Hehe