Aside from the fact that 99% of the vegans I know do it solely for sake of hipness (like riding fixed gear bikes... that will be a future post) there are some vegans who are attempting to make some social statement about animal rights, economic impact, or general health reasons. The fact is, these vegans are so infatuated in their own bullshit that they fail to realize that the harvesting of crops leads to the deaths of THOUSANDS of land dwelling mammals. Studies have shown that areas that produce crops commercially have devastated the surrounding ecosystem.
So unless you ONLY eat foods that you grow yourself, shut up.