Handling family overstepping?

My husband's family is very eccentric to say the least. His father is very kind and listens, but his mother and sister are very pushy and invasive (both came to stay a week with us unexpectedly the week I had my first baby, try to take my kids and feed them things I'm not comfortable with, etc.) A few weeks ago my husband took our oldest (2) to his family's house for dinner, which is pretty normal. They're pushy but his dad keeps them restrained. My son is not potty trained. At all. He goes on the toilet when he asks to, but I'm not potty training him fully yet as he doesn't seem ready. My SIL took him to the bathroom while my husband was talking to his mom and forcibly took his pants and diaper off and held him down on the toilet while he was screaming for me and my husband. My husband came in and took him back and yelled at her for doing that, as my son has only met her a few times and would not at all be comfortable asking her to take him to the toilet (especially since he hadn't asked at all). His sister got upset and basically called my son a "brat" and a "fucking annoying crybaby" and kept berating my husband about babying him and telling him that we are bad parents. He asked me to text her and reaffirm that we aren't potty training, so I politely texting her, thanking her for taking initiative but saying we aren't quite ready for that step and I hope she doesn't mind giving him space (was a lot more kind than I felt, I was LIVID). She responded telling me that she assumed my husband told me that she abused my son and hoped he wouldn't bring my son back to see her until he wasn't going to be an annoying baby and crying. I'm honestly angry. He is in diapers, we never once told her he is potty trained, he never asked to go, etc., and now he refuses to go to the bathroom at all and cries when I go to the bathroom. I know it wasn't intentional, but I have absolutely no desire to keep letting her see him if she is going to treat him poorly and verbally abuse my husband and I. Am I in the wrong? via /r/Parenting https://ift.tt/32Y1q3U