Need some help on telling hospital visitors a small rule I have..

Anyways this is my second baby first one is 3 now and when I had him in the hospital and I had visitors I asked everyone to please not give him and kisses on his face or lips. Well I also told SIL and her husband since they LOVE doing this and even after I asked them not to they still did it so I won't lie I got a little upset and asked again with maybe a tad of attitude 😅.... 

Well after that SIL and her husband and other family members have pretty much hated me and think I'm just "to much". 

I swear I'm not exaggerating though they will like full on HUGE sloppy lip kiss a tiny newborn and continue doing it over and over. Both of them. I'm finally in a better place with them  after having so much problems with them and just don't want to ruin things.. But I have this simple rule again where I want no lip kisses or on baby girls face and don't know how to tell them without anyone getting mad or upset. SIL is pregnant and due in January and she gets very emotional over anything and as much as my bf doesn't care if she gets mad and emotional I do because I really don't want problems with them again. So I just don't know what to do. Maybe there's a nicer way to ask? Or something? Any advice ladies ??