When Moses returned to the scene, his people had already reached their lowest point. They worshipped idols, spoke evil of one another, and strayed far from the path of their ancestors. Perhaps he should have rebuked them, saying, "Repent, sinners, or you will die!".
But he didn't. Instead, he told them how God loved them and felt their suffering. How He would perform miracles for them, give them freedom, and a wonderful future because of His love for them.
As a rebuke, Moshe left that to God. "How have You mistreated Your people?" he demanded.
If you don't like someone's lifestyle, do them a favor, lend them a hand. Once you've brought some positive changes to their life, then you can urge them to change their bad habits.