You are referring to Isaiah 5:20, Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter!
It might be important to note that the book of the prophet Isaiah starts by establishing the themes of judgement and subsequent restoration for the righteous in terms of Israel. So, in this verse we see one of many where Isaiah is describing, or establishing, Gods judgment upon the nature of sin, or sinfulness, the lost in terms of examples of nature and such; IE in this case, those who call evil good, and good evil.
Some examples? Perhaps examples we might see today? We don't have to look too far. Cultural Relativism is good place to start and you can see it all around us. Gay marriage is a good example. If you call homosexuality "evil", people are going to take quite an offense to that. They may confuse such a statement as hate, as we see in the Westboro group, but if you call gay marriage a good thing you will not have much throwback about that in our culture today.
I purposely picked a controversial example like this because I think it best to speak about the word evil. Typically, the bible refers to evil as anything not of God, and Good as everything of God only. Jesus called people in general "evil". The bible makes a clear distinction between good and evil in this way, where as we tend to attach much more strict terms to the word evil.