Its easy to say mean things to or about others. Some one cuts you off on the highway and you call them a moron. A co-worker does something to annoy you and you complain about it under your breath or to another co-worker. You disagree with someone's politics or views and you call them idiots or worse.
This is human nature, but if we are following God should we be like that? According to Ephesians 4:29, the answer is no. We aren't supposed to tear down others. We are supposed to build them up.
There is a few reasons for this. The first is obvious. Its what God wants us to do. The other reason has to do with us. The more we tear down others, the more we will view others negatively.
Conversely, the more we build others up, the more we will view them in a positive light and the more we will find ourselves loving others, which not only is what God wants us to do, but it also makes it easier to share what He has done.