Non confrontational people, how long did you let things slide until you snapped?

They are very good at hiding how narcissistic and passive aggressive they are. They act totally different when they are separated so when they are together, it’s like a tag team. They never make comments to me around my husband so he has never witnessed it. Yet when I voice my feelings, he immediately wants to say something to them, but I stop him because the moment has passed and they would know it came from me ‘bad mouthing’ them and play victim and I rather him stick up for me in the moment, but they are very cautious with who is around when they say things. Is that manipulative of me to stop him? I have completely cut off his mom’s side due to constant disrespect by just not going to occasions involving them. I’ve kept my mouth shut for 7 freaking years and have always respected her as his mother, and never wanted to put him in a situation to choose sides. However, I’ve had enough and I’m fully prepared to defend myself when the next time comes.. if I don’t chicken out.