"Either make the tree good, and his fruit good; or else make the tree corrupt, and his fruit corrupt: for the tree is known by his fruit. O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh." (Matthew 12:33-34)
It's easy to see this as one of Jesus' "falsifiable" statements. A statement that is capable of being proven false. I suppose one would have to see to the heart-depth of the interlocuter in question--every time--for His declaration of "out of the abundance of the heart the mouth speaketh" to be proven, every time. I struggle with this statement a lot when I think about people who profess the name of Christ yet don't act in accordance with His heart. Understandably, people struggle. And out of all those I count as brothers and sisters in Christ, comparatively few do I ever have extended conversations with. It runs the gamut from people I encounter about town and in society, who I'd never peg for Christian--not because of appearance, but because of attitude. All the way from that to those in my church. I, too, meet people who don't think I'm Christian. If I bring up something spiritual or Christian-sounding, they're shocked. What can I say? I've been affected by what I've been affected by and maintaining my label (Christian) and my heart has been the struggle of my life. But this statement. The point is, just because someone "nameth the name of Christ" doesn't mean they're Christian, doesn't mean they know Jesus. Yet, if I were to take His words out of context, it's almost as if the concept of "lying" has been negated.
"Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are His. And, Let every one that nameth the name of Christ depart from iniquity." (2 Timothy 2:19)
"Whoso boasteth himself of a false gift is like clouds and wind without rain." (Proverbs 25:14)
A psittacism is the same as "parroting back" (the Latin root for "parrot"). A mindless repeating of something someone's heard and, maybe, sounds good or true. Best to sound true if you're a Christian, by the way. And there really isn't much more to say on that topic. I find that so much of what is bandied about in the world is without any real heart-depth. Empty words, Christian or non. The motive, the why. Paul qualifies the Christian's self-declaration with a spiritual Spring cleaning. Make sure your heart is right with God if you're going to gab and gadabout. St. Francis says to "Preach the Gospel at all times and when necessary, use words." The world needs more Christlikeness in action, not in word.
Jesus continues, "a good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things. But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment. For by thy words thou shalt be justified, and by thy words thou shalt be condemned." (12:35-37)
It would seem Jesus is now referring to the words spoken (to Him) on "the day of judgment". A time when one is unable to say anything but that which is at the depth of one's heart. A hard word to be sure. All the more reason to "sanctify the Lord God in your hearts" (1 Peter 3:15), in mine. If the mere mention of Jesus, in many circles, is seen with skepticism and derision, is it the Christians' fault by and large? Not completely as "it (the world) hated me (Jesus) before it hated you". (John 15:18) But I find that a negative and loveless representation of our Lord makes for a wrong image of Christ.
John says this: "My little children, let us not love in word, neither in tongue; but in deed and in truth. And hereby we know that we are of the truth, and shall assure our hearts before Him. For if our heart condemn us, God is greater than our heart, and knoweth all things. Beloved, if our heart condemn us not, then have we confidence toward God." (1 John 3:18-21)
Here's the thing. If you believe in Jesus, you can trust your heart. Because your heart is the same as His. As yet, we may not be able to trust our minds. Because it's our life's work to reorient our mind in light of His. If you find conviction in the areas of truly living out your faith, know that God is greater than that feeling and He's calling you higher. He'll help you see things in His light. And the more your heart is in line with His, the more your words will carry the weight they're supposed to.