How to handle MIL and family??

Tuesda
I am needing some advise on how to handle this situation going forward. I am a FTM and know it might seem small but I think it is a respect thing. Me and my husband went to my MIL for her to see the baby. He is 5 weeks and right now I still want people to wash their hands because that is what I feel comfortable with. Well MIL told me no and picked my baby up. I was so pissed and walked out because I did not want to start a scene. My baby started crying I took him not before letting her and her sister know that they would need to wash their hands and need to respect my decision. The sister had the nerve to bring up my mother that is deceased and said would I ask her to wash her hands. That really pissed me off. She had her nerve but I told her she would respect my decision. My parents do not treat me like a child they respect me as an adult (did not say this part but now that I am typing this I thought about it).  The thing about our relationship is that we have never liked each other and she has always been disrespectful to me while I respect her. I am really getting tired of it and I feel like if I do not speak up she thinks she will be able to do whatever she wants to do regardless of what I say as he gets older. Please let me know your thoughts. Am I wrong for the way I feel???