MIL baptizing baby without consent

My SO and I are not religious people at all. I’ve never gone to church, but he was raised catholic. He no longer identifies as catholic and doesn’t attend church. His parents are catholic and mother still goes to church, his siblings as well. All the other grandkids have gone through the baptisms and things of that nature. Anyways, how would you feel if you found out your MIL had baptized your baby behind your back?