I passionately HATE this for a number of reasons.
1. Those ear guns at the mall cannot be properly sterilized. The people ramming them into kids' ears haven't been properly trained, and unlike a piercing done with a hollow needle, those guns press metal through the ear traumatically instead of making a space for the earring that can heal properly. If an adult wants to go the cheap route, and get a mall piercing, that's their business. But, a parent's most important job is to protect their child. It's an uneducated and potentially dangerous choice health-wise.
2. Most moms want this done to keep their girls from being mistaken for boys. At baby age, who the fuck cares if a stranger doesn't know which genitals your kid is packing.
3. Pain for the sake of cultural norms should be an adult decision. (Before anyone asks, yes, I'm also against circumcision.) Inflicting pain on a little girl so she looks cute to your friends is selfish. There's no way a baby cares whether her ears have bling or not. It's something the parent does for him/herself. Selfish and parenting should not mix.
4. Who knows if your kid is going to want those holes in 10 years?! And after a decade, they're stuck for sure.
That said, my trashy mom pierced my ears at 6 months old. God forbid the good people of Flint, Michigan think we were too poor for bling. I'm just lucky she didn't do it herself.