Human nature revolts against such a crime.

A frown may express anger or displeasure.

Stop it! You're making her feel uncomfortable!

The concept of "Tatemae" tends to be misunderstood as lying. But I think it's not lying in the sense of deceiving others, but rather as a way of respecting others' differences in opinion without making them uncomfortable. It's a cultural aspect stemming from how Japanese people tend to avoid arguments in favor of keeping the peace.