Whether you believe there is a God or not, the majority of the human race appears to have an intrinsic sense of right and wrong. We may disagree over the exact nature of what this is, but on a personal level most people have the sense that at some point in their life they have done something morally wrong. And what gives people this sense of wrongdoing? It may be seeing the effects of an action, it may be a feeling of regret or shame or guilt. So, whether you follow Jesus or not, we can all start from common ground on that point.
Are there more serious things that we can agree on as to their being definitely wrong? Murder? Adultery? Theft? But then again is it wrong to execute a murderer? Is it wrong to thieve to feed a starving baby?