Remember that *evil* is an English word. Spanish has *malo*, which can mean milk that has gone sour or murder. At the end of la Dolce Vita, an Italian says, in English, "It's evil" because he doesn't have anything in his language to express what he means. The English *good* has the same ambiguity.
It's one thing to say there's a relationship between contrasting pairs, shades of gray between black and white, and another thing to say the contrasts don't exist. This is something some Buddhists fail to see. Up is not the same thing as down. There's a difference between goodwill and malice. (A translation of the Kalama Sutra quotes the Buddha using the word *malice*.) Buddhists don't use the word *sin*, because they generally prefer to attribute misdeeds to ignorance rather than malice and because the word has baggage from Judeo-Christian tradition. For example, in the Bible, murder is sin, likewise women wearing red dresses. Christians say that babies are born sinners, whereas Buddhists say they are born with Buddha nature, although ignorant and sorely in need of wise instruction.
So, yes they are opposites, but be careful about name-calling.
"These things happen because of their ignorance of what is good and evil."
- Marcus Aurelius
"Forgive them, for they know not what they do."
- Jesus, quoted in the New Testament