Good versus Evil
The Struggle Between Good And Evil is a classic narrative in storytelling and narrativization. As a metaphor, it is often very useful and sometimes quite reasonable. However, this kind of narrative also lend itself to narrativism that gloss over the problematic aspects of those constructed as "Good" as well as the more humane aspects of those categorized as "Evil". This can easily go all the way to to outright demonization & dehumanization of those human beings categorized as "evil", opening the door for not only discrimination and persecution but also outright genocide.
Thus, the concepts of good and evil are highly problematic. In fact, it might be reasonable to regard the dichotomism of "good versus evil" as being inherently... evil.
A more specific problem with the concepts of "good" and "evil" is that they only communicate the fact that we strongly like or dislike something, being far more unclear as to why and how and in what way.
If you think something is evil because it harms people, it would usually be more constructive to call it harmful - and explain how and why it is harmful. If you think something is evil because it does not conform to your political or religious dogma, it would usually be more honest as well as constructive to say so outright. Calling people "evil" may be more efficient in a purely demagogic sense, employing it as a "thought-terminating cliché". However, you should see such tactics for what they are - preferably recognize when other people are using them, as well as abstain from using them yourself.