This is what God says about our speech - going against His commands is sin, plain and simple.

Colossians 4:6 Let your speech be alway with grace, seasoned with salt, that ye may know how ye ought to answer every man.

Salt is a preservative that prevents corruption.

Titus 2:7-8 In all things shewing thyself a pattern of good works: in doctrine shewing uncorruptness, gravity, sincerity, Sound speech, that cannot be condemned; that he that is of the contrary part may be ashamed, having no evil thing to say of you.