Comes from "fascist man", generic name used by many trolls abusing the Yahoo! Answers France service. There are actually hundreds of Yahoo! accounts using this name.
Fachoman was probably invented during the 2007 French elections. The person using that username won a troll contest. Since then, Fachoman appears every two weeks or so, posting dozens of racist questions and mysteriously disappearing.
Fachoman is part of Yahoo! answers popular culture. His questions are always receiving a lot of answers.
1) Create a Yahoo! account
2) Fill a Yahoo! Answers profile with the name "Fachoman"
3) Upload a nazi avatar (Hitler or swastika)
4) Post racist questions
6) Proft !