A corporation is typically considered evil if any of its employees are evil. If you're feeling generous, maybe you'd relax that to a small group of employees, say 0.1%. For example, AIG employs close to 100,000 people, yet I doubt that more than a few hundred were involved in the mortgage derivative mess. Yet we still pretty much universally revile AIG.
Say that 1% of people are evil. It's totally reasonable to expect an individual to be non-evil; after all, 99 out of 100 (in this model) are.
But then extend that out to a large corporation. The probability that you'll find at least one evil person in a startup of 10 is (1 - .99^10) = 0.095, or about 10%. The probability that you'll find at least 100 evil people in a corporation of 20,000 is (1 - .99^19900), which according to Google calculator is 1, i.e. virtually certain (there's some round-off error there, but you get the point). In order to have any fighting chance at being non-evil, a large organization has to actively seek out evil and eject it from the organization, simply because the organization as a whole tends to be judged by its worst members.
"Never attribute to malice what can be explained by math." - PG