When people meet somebody who hurts us or just behaves in an
inappropriate way, we usually think that the world would be so
wonderful if all people were good.
How do you know that hurting you was the person's intent and not just simply a mistake? And if you perceive an action as inappropriate, maybe you have a too strict of a view of how other people should behave?
Is e.g. Marilyn Manson an artist who expresses himself or an inappropriate human being that should be banned to perform an his CD be burned?
Yet let's assume that all people could act good (for whichever definition of goodness you want to apply):
If everybody was acting good then there would be no need to label humans in categories of good and bad behaviour. In a world without an illness the term "health" would lose its purpose and we could do without the label.
How would you find the the notion to wish for an illness in such a world just so one can make the distinction between healthy and sick people? From a philantrophic perspective that seems absurd.
I hence would reject the notion that it would be good for some to be evil.
The real question that it is hiding is what kind of behaviour is deemed good? And how to define what is evil?
As there is no universal understanding what those terms mean, unless you are operating under the premise that a divine being commands what ought to be good and what ought to be bad, it is not possible to declare a state in which all people would be good.
Also, is an action in itself evil or does it depend on the intent? Is it always evil to steal or is something else if you steal expensive medicine for a sick friend of yours?
Human values are changing over times and so the perception what is considered good and bad does so as well.
The statement "It's good to be bad" is only ever used by Disney villains that are bad simply for the reason of being bad. No human that has, from our perspective, committed attrocities ever sees onself as the bad guy, the think they are the good guys.
That is also why I would opt for not using the terms good and evil to describe human behaviour. We should ask ourselves in what kind of society we want to live in and what methods we want to use to achieve it, completly without obscuring the matter with a fuzzy notion of good or evil.
Some societies have declared war to be a central part of their culture, and a hero death was the most respected one. Other people want to live in a peaceful way together on this planet and have as much fun while being here and then die in their sleep.