If someone is evil-minded, it is not that they once had a bad thought. It is about the kind of mind they have: immoral and cruel, and likely to look for ways to hurt people or wreck things. The word judges character, not one action. It is strong and a little old-fashioned; younger speakers often reach for malicious, twisted, or cruel instead. Though actually, -minded here just means “having this sort of mind,” the same building piece as in open-minded or like-minded — but those are mild, and evil-minded is not. Do not use it merely because you dislike someone’s opinion. That would be heavier than the situation deserves.