To question “can there be good without evil” implies that they are fundamentally different in their true nature and that could take a lot of justification. It really goes back to the first question of who gets to define good and evil and that could be more complicated than can there be good without evil.
Even though there seems to be a social conscience of what good and evil are they are still relative terms. Relative terms that we have assigned using our senses and experiences. We may need good to describe evil and vice versa but that could be just a nomenclature issue and what part of a name encompasses an object?
Maybe good and evil are just different parts of the same thing just seen in a different relative light. The question then could become can we alter how someone receives/perceives their inputs in an effort to alter their perception of good/evil?
But in a lighter note the concept that good and evil are really just two parts of the same is presented in the clip from Dark Crystal.