In my devotional time, I've been reading James (one of my favs- I can't read it enough) and I was struck by this verse: "If anyone considers himself religious and yet does not keep a tight rein on his tongue, he deceives himself and his religion is worthless." -James 1:27 (NIV)
This is pretty powerful and there is not room for much negotiation. James 3 goes into much more detail about taming the tongue.
Proverbs 12:18 says, "Reckless words pierce like a sword, but the tongue of the wise brings healing."
Gossip and slander are detrimental in general, but especially for the church.
Everywhere we go, we are to be a representation of Christ. Non-believers should see the way we act and speak and know there is something different in our lives- something they desire to have as well. How are we representing Christ if we are talking negatively or behind the back of someone made in his image? How can we be inviting friends to church one minute, then participating in the latest gossip the next?
Obviously nobody is perfect and situations arise where we lose control of our tongues. I am definitely guilty of this. I let my emotions override my desire to glorify God. In realizing that, I pray for the ability to refrain from gossip and glorify the Lord in all ways-especially through speech.