Difference in opinions with in-laws for raising a baby

My mother-in-law is a very opinionated woman. My Approach with her is that I first talk about articles I've read or studies that have been done or a piece on the news that I watched that relate to a boundary or rule that I'm wanting her to follow. I make sure that I have a reason for the rules I'm making and that I can clearly communicate the benefits of my choice and the negatives of the other options. For my mother-in-law, that works.

Yes this is a tough one, my MIL kept kissing my baby though I had asked them not too, then we were all having dinner and the convo led into baby stuff and health and I repeated why I don’t want anyone to kiss my baby, I even had a few vids saved to show them why incase they don’t believe me, it’s tough navigating in laws, the partner needs to help more so here too,

I have a friend who also has a very opinionated mother-in-law. Using experts to support the parenting choices she makes doesn't make a difference to her mother-in-law. So she simply States the rule and the only explanation she offers is "we're his parents and that's the decision we've made". She still finds out about her mother-in-law doing things behind her back, like offering more sugar or screen time then they allow. But she's accepted a certain amount of non-compliance because they offer free childcare