Why do we expect Christian behavior from the world?

It amazes me how we expect non-Christian companies to act like they are run by Christians. Why would we expect Walmart to instruct it's employees to say merry CHRISTmas if they are run by people who don't believe in Christ. Would our time be better spent building relationships with not yet Christians than fighting with them over "Merry Christmas"? Showing love not disdain. I seem to think so!