You don't have to tell someone when their shoes are ugly.
But you should tell them when their practices are impairing others in performing their job, or wasting money, running off business, et c. You tell them before the boss does. If you *are* the boss, you should know how to handle it. If the truth hurts them, *they* have a problem. Adults should be able to handle embarrassment. Children would shoot you the bird and run away.