Curse words are bad for human life because they seem like tools of cognition, but they aren’t. When used as words, they can only confuse and mislead you.
However, sounds that aren’t words can be very useful—they are perceptual evidence that we use in our reasoning. We identify groups of perceptions by differentiating them from other perceptions, integrate them into concepts based on their similarities, and assign words to represent all of concretes of that group.
So you have many “noise” experiences from yourself and in human interactions, identify some as happy, and now you have a useful new tool of cognition in the form of “happy noise”. With additional experience, you can refine that into many sub-concepts, like “pleasurable moan”, “contented sigh”, “silly giggle”, and so forth.
Curse words are different because they are just noise. If I say “happy noise”, you know broadly what I’m referring to. But if I say the word “fuck”, you have no idea what that word means—you would have to make guesses either based on the surrounding words that have semantic meaning, or based on how I said it using your conceptual knowledge of the kinds of noises.
That’s why you see curse words used in every kind of context as undifferentiated noise.
With my kids, I tell them that using any word they don’t understand is a curse word. It hurts their own life if they make the noise of advanced words they don’t yet understand, because it introduces ambiguity into their thinking.
For more information on the role of precepts and concepts in human cognition, I suggest reading “Introduction to Objectivist Epistemology”.