How do you deal with people that argue against your parenting choices?

We spent Christmas at my in laws house and my MIL has once again brought up getting my daughter's (6months) ears pierced. My husband explained that we want to wait for her to ask and shows interest in having them pierced. MIL says she "will wait for her to be out of that thing(bucket car seat) to bring her". So her plan is apparently to take my daughter to get them pierced with her friend who has already done it to her own grandchildren without permission from the parents to Claire's. Of all the places in the world she wants to take her to a place that uses a piercing gun. She didn't take us seriously when we explained we would take her to a professional when the time comes. I'm struggling with even feeling comfortable with unsupervised visits in the future because of this. I never thought this would be the kind of crap I'd have to deal with as a parent. via /r/Parenting http://bit.ly/2GEe54D