Update! MIL called me a bastard because I said no kissing the baby

My MIL called me a bastard (in spanish) because I made a public post on Facebook, addressing everyone, that I do not want anyone kissing my baby when she is born. Of course my own mother and my MIL are both very upset about this. My SIL even made a remark that she would just ask my fiance, who responded with "Hey, don't ask me. I'm doing whatever she(me) wants." To which my MIL said she is going to kiss the baby anyways and doesn't care. As for my parents, they say the baby needs to build up an immune system so kissing won't hurt her. I'm very upset that everyone is taking it so personally because I always thought that everyone would be understanding. I've seen so many posts about babies getting RSV and it scares me but they all say I'm too paranoid and read too much stuff on the internet 🙄 My fiance's family is flying down during babys birth but now I don't even want them there. They're going to stay with us for 3 weeks and I'm seriously dreading it now because I know they'll kiss my baby like it's not a big deal. I have no idea what to do. My parents will eventually get over it but my fiance's family is taking it very personal and says I'm being rude.

Update:

Thanks for the advice everyone. I'm going to stand my ground and be strict with the no kissing. I asked my fiance to be strict with his family when it comes to kissing and not just make me deal with it and he agreed. As for them staying, I never invited them 😥 They all invited themselves and my fiance just went along with it because he wants his family there for the baby's birth. If it was up to me I wouldn't want anyone around but I can't refuse his mother. She says she will help with cooking and cleaning so we will see. I definitely will not tolerate her taking my baby and telling me what to do. We also talked about just his mom staying with us and his sisters and BIL getting a hotel so we aren't overcrowded. Baby isn't due until March so I'm hoping that will be enough time for them to get over not kissing the baby.