The concepts of Chillul HaShem, profaning God’s Name, and its opposite, Kiddush HaShem, are part of this sidra (Lev. 22:32).
If we sanctify God’s Name in public, that is somehow easier than doing it in private. When people are watching we tend to be careful about our conduct. Yet Pir’kei Avot warns us to be scrupulous about it in private too: “Whoever profanes the Name of Heaven in private will suffer for it in public, even if it is done unintentionally” (Avot 4:5).
What we do in private is often rather relaxed. “No-one is watching,” we say, “so I can let myself do what I would avoid in public”. The truth is that there is always Someone watching – the Almighty.
But apart from this, abandoning one’s standards in secret is a form of self-deception. The issue is not merely whether anyone else is watching but whether I really believe in my moral standards. If I do, they apply even when it seems that no-one else is around.