I'm going to tell my daughter I'd kick her out if she got a tongue piercing
Why wouldn't you be willing to raise your child after she got her tongue pierced?
Because I think tongue piercings are disgusting and wrong.
Even if you were just making threats, it is wrong to kick a child out on her own. Your daughter will not be able to survive on her own, so you should be willing to take care of her, even if she breaks your rules.
I just want her to follow my rules no matter what.
Your daughter is probably old enough to decide if she wants her tongue pierced or not. You should just respect her decision and keep taking care of her.