Breakfast with Solomon - Proverbs 25:5
"Take away the wicked before the king, and his throne will be established in righteousness"
This verse proves that environment does impact everyone – even the righteous leader. If you are constantly surrounded by those who live outside of God's moral boundary structures, then you will begin giving in to those wider moral boundary ideas. If, however, there are not people who are lying, stealing, coveting, committing adultery, and being physically violent with others around you, then you will not be influenced to excuse these kinds of things or participate in these things.
When we are raising our children, this is why we should make sure that the environment that surrounds our children does not baptize them in evil. Instead, they should be incubated in righteousness and not be pulled toward wickedness. While we cannot protect our children from all exposure to evil and sin, it is unwise to allow them to live in the midst of that which is wicked constantly. The danger is that even in good Christian homes, children can have daily access to wickedness through television, computers, internet, video games, etc.
Notice that this is about the leader. The leader cannot afford to build an entourage that is wicked, or the good that his leadership could do will never take place.