Kids tell it like it is. They don't understand sugar-coating or lying for the sake of self-benefit. If they see something, they say it or ask about it. We should all be so smart.
As adults, we learn tact. We learn to be more careful with the feelings of others rather than just blurting things out, but it's important that we remain honest while doing so. As adults we often become too careful, too afraid to offend a person or group, and therefore water down our thoughts or even create a lie in their place. While I am all for saving the feelings of others, I am also a believer that a painful truth (that will help someone grow) is more desirable than a comfortable lie.