I think the idea is that "evil" is a relative term and it relates to morals, not ethics.

http://www.diffen.com/difference/Ethics_vs_Morals

I think the point which the parent is trying to get at is that he should not be expected to follow rules whose premise he disagrees with. People can call you whatever they like, but the question is whether you should allow their moral or ethical norms to affect your actions.