Proverbs 15:1

A soft and gentle and thoughtful answer turns away wrath, but harsh and painful and careless words stir up anger. 

How we speak to each other is important because we can cause an adverse reaction from others.  Have you ever noticed when someone is in a bad mood and needs a spark to make them angry?  The person may already have a negative internal dialogue, and when more negative words are spoken to, it gets worse.  A gentle response can put out the fire before it burns out of control.