oh.... in laws...

So I have ALWAYS thought the world of my in laws, and am so stuck on what to do.... I have always thought they loved me too, but I guess not. I walked into their house the other day and noticed they were talking awfu loud. I get to their mudroom area and hear them talking about me. I hear my fiance's grandpa say "She is just a snatch. -Insert my name- is just snarky bitch, and sarcastic too." I REALLY have an issue with this because then his grandma messages me saying I took it all wrong and had no clue what I heard. I heard everything. Even when I walked into the living room(I didn't stop in mud room I just walked thru) the grandpa said "shit and there she is." He wouldn't even look at me. I'm really afraid of what they are going to say about my son after hearing the way they talk about me and my man. I don't even want them asking about my son at this point. 😔
Should I keep my son clear of them? I just want nothing to do with them after this. I thought the world of them and without batting an eye they could shit talk me.💔