My Daughter Wants to Pierce Her Tongue

Explaining to your daughter why you think a tongue piercing is a "bad idea" --possible health issues (e.g., nerve damage), aesthetics, being labeled as a "freak," etc. -- is easy. Convincing her not to get it done for any of those reasons might prove more difficult. The fact is that her tongue may be just fine (health-wise) if a seasoned professional pierces it under strict hygienic conditions. As far as how this looks, she can cite the "beauty is in the eye of the beholder" adage and you are left with telling her that you think she must adopt what you think are appropriate standards of beauty, regardless of what she wants to do with her body or how she adorns it.

Her response to your fear that she might be labeled negatively because of this piercing could be that you have taught her not to let the superficial, baseless stereotyping of others carry any weight with her. She may want to pierce her tongue partly because her "hip mom" has a pierced navel, but I doubt that is her major reason. Notice she is piercing her tongue, a more blatant move than navel piercing, which people do not usually observe in everyday life. I don't think she wants you both to be twins in this regard.

I would calmly make your arguments against the tongue piercing, being careful not to shame or blame her as you explain your disapproval. Have a discussion -- don't lecture her. Then, if you feel that she has argued reasonably for why she could safely have her tongue pierced, you must decide whether supporting this or attempting to forbid it will be in your daughter's best interests and in the best interests of your relationship with her.