B..
You have to decide what it's worth to you.
It could be that people are comfortable with the passive aggressive stance that they are taking (hating the behavior, not confronting, talking about it afterward). If you do speak up, you have to prepare for shock and maybe some anger that you would rock the boat.
It could be that you do not fit in. I married into a family with that kind of dynamic. That was not going to fly with me. You understand this is the way they handle anger. I hate passive aggressive behavior. You may want to bow out now. I did not. Yes, there were times of sharp conflict and uncomfortable silences. But in general, we found a place we could live with each other.
In fact, the one I had the biggest conflict with, became a great inlaw. The one who could only say good things to my face and talk about me behind my back, became the very worst kind of inlaw. So, you never know.
Me? I'd have to shake things up before I jumped in to marriage.