Gates is a weird figure - I don't think he's actually evil (nowadays), because evil implies malicious intent. Rather, he unintentionally commits evil actions (those which harm people and if committed with full understanding would be unambiguously evil) as a result of his own personal extremely warped values. The guy thinks patent law is the highest moral good, so the millions of people who don't get vaccinated as a result are either forgotten about or a necessary sacrifice for the societal good of protecting patents (which he might justify as making these sorts of innovations possible in the first place - demonstrably incorrect, but good luck getting him to listen to anyone who might tell him that).
tl;dr you can't be evil by human standards if you have alien blue and orange morality.