Atheism and Ethics

[Lucian]

As for lying, I would say it's only wrong when it causes harm. But you could also be a rule consequentalist* and believe it's wrong, as a general rule, to lie.

*Or a deontologist

I think that Hugo Mercier has some good stuff on lying in his book Not Born Yesterday. Communication and cooperation is dependent on trusting what someone is saying, with varying levels of epistemic vigilance. The more someone lies the less likely we are to trust them and it makes our engagement with them unproductive. If that happens too widely societies would break down. He likens it to signalling in the animal world, with stotting by antelope not just being a “hey, I am super fit so don’t go for me”, but also as a “we have seen you” signal to the predator telling them that they are unlikely to be successful in the hunt. Should that signal prove too unreliable, the purpose would be done away with. 
Interesting read, especially with how our faculties derived from originally small groups cause havoc in the modern world