In Mark 7:20-23, Jesus explains what defiles us. What we say with our mouths, He says, reflects whatever is in our hearts and therefore will eventually spew out of our mouths. This is one reason why “four-letter words” are wrong. When I taught teens, some agreed with the late comic George Carlin’s erroneous position that words are just words and none are wrong to say.
This raises a good question: What really makes the “F-word” wrong? I’ve always maintained that sexual intercourse between two humans in love with each other and married is a very special moment. God joins us in a holy soul-tie to one another through this act. With humans, sex is more than a mere physical act. It is NOT the same with animals because there is no love or soul-tying happening. By reducing the human sex experience down to a word that is often used in anger, rebellion, gross exploitation of women, or debasement to an animal level, it becomes quite bad (foul, perverted), certainly not neutral as Mr. Carlin asserted. Other words are wrong because of gross connotations they carry. Every language has them. If they spew out of our mouths, then what is in our heart? Ouch.