I would make a formal complaint to the boss. If that doesn't work, it's time to fight fire with fire. Some (tongue in cheek) suggestions:

1) Discuss, at length, the medical procedure of a vasectomy. "Wow, guys, I really find this interesting." Also mention what a "Eunuch" and a "Castralto" actually is.

2) Describe, in considerable detail, the story that was posted in Cat General about the cat that bit his owner's testicles.

3) Discuss with each co-worker why his car is a total piece of crap. Include reasons such as the car being underpowered, mostly driven by hair-dressers, favoured by rice-boys. You may need to do some research on this one if you are not a girly rev head like moi! If they have a hot car, praise them for their choice, but inform them that the car does not even come close to accounting for their less than favourable attributes.

4) Leave a magazine on their desks with ads about "viagra" and "love troubles" circled in red pen.

5) List all the reasons why they will never score with Liv Tyler, Drew Barrymore or Natalie Portman.

6) Engage them in a discussion about their hunting weapons. You will definitely need to do your research for this one. Then, armed (no pun intended) with the necessary information, discuss with them why their gun is usually the weapon of choice for 13 year olds shooting tin cans off a fence.

7) And finally, tell them that people who fantasise about or are activelly cruel to animals were usually pryos and bedwetters as childen. Mention that they often become serial killers. Make creative use of eyebrows work in your favour!