kids kissing grandparents

Hey guys I need some input. I personally decided before I even had my daughter that I did not want her to kiss anyone on the lips other than me & her father. It's just a personal decision & maybe it's because I only was taught to kiss on the cheek. I caught my mother in law kissing my 5 month old the other day & I kindly told her not to do it again. Well last night she was doing it again& I told her to stop doing it... AGAIN. there response was "the baby was kissing us we weren't initially kissing her".  I of course was mad because regardless if I tell them to do something they need to do it. What makes it worse is that my husband is on his parents side (however he still had a talk with them & told them not to do this). Does anyone agree with me or my in laws???? Advice is appreciated