Buying like-new consignment clothes for infants?

I had a little argument yesterday with my MIL when I mentioned an awesome store I found for babies that is consignment. Everything isn't second-hand, but the ones that are are in mint-condition and very clean. Barely used.

She stopped dead in her tracks and told me that I am not allowed to put resale clothes on my child. (I'm pregnant right now).

First of all, I see nothing wrong with resale items if they are CLEAN and fine. Babies barely wear their items sometimes and grow out of them quickly. I see nothing wrong with this. My husband agrees with his mom, but my mom agrees with me and thinks it's totally normal. My best friend agrees with me.

What are you opinions?