It's very common for people to think that evil doesn't actually exist in of itself. Rather, like a hole in your shirt is just an absence of fabric, some would say evil is just an absence of good. Of course that doesn't mean there is no truth about evil, or that it wont affect your life. A large hole in your jacket, despite not being a thing in of itself, will still make you miserable on a cold, wet winters day.
But there is an obvious problem with this view, in that it would require all things (at least within the relevant domain) to be either good or evil. You can't have shirts that are neither whole nor have a hole, but you can have actions that are neither good nor evil—in fact most actions seem morally insignificant. What could be the moral value in cutting your grass, or eating a cheese burger? If you find some morally significant feature, one can always easily stipulate a scenario in which that feature isn't present.
And so defenders of this view must embrace the implausible and maintain that every action, no matter how seemingly insignificant, has moral value to some degree. This is why I favour theories of moral ontology on which good and evil are both real in a robust sense, neither being an absence of the other.