The thing is atheism isn't that big of a thing yet. Someday, when you've got a lot of people that are atheists, you'll start getting some stupid as **** atheists. Right now, we only get the occasional Unabomber, dictator, or ecoterrorist, because there's really only a very, very small population of atheists from which to draw. But crazy comes in all stripes. There have been dictators that were atheists, who killed those that opposed them to create what they viewed as "a better world." The Unabomber believed technology was harmful to humanity's future and the environment, so his targets were selected accordingly. Ecoterrorists tend to target development projects that they disagree with, and have killed people in the process. Ecoterrorists (and their animal activist brethren) tend to be white, educated, and non-religiously affiliated.
In 2008 the Federal Bureau of Investigation said eco-terrorists represented "one of the most serious domestic terrorism threats in the U.S. today" citing the sheer volume of their crimes (over 2,000 since 1979); the huge economic impact (losses of more than $110 million since 1979); the wide range of victims (from international corporations to lumber companies to animal testing facilities to genetic research firms); and their increasingly violent rhetoric and tactics (one recent communiqué sent to a California product testing company said: "You might be able to protect your buildings, but can you protect the homes of every employee?").
Give it time. Atheists will catch up when their numbers do. Because at the end of the day, evil isn't about religion or political affiliation. It's part of human nature.