Weddingbee boards

I have a friend who I have known for 6 years and who is going to be a bridesmaid in my wedding. She is recently engaged to a man she's known for a year and a half. We'll call her B and him D. My problem is with D. I've never said or done anything to offend him, but I've found out on two separate occasions that he's talked bad about me. 

The first time was when B and D were hanging out with a mutual friend of mine. The friend is much closer to me than them, so she felt the need to let me know that D was talking bad about me behind my back. At the time, my FI and I just got engaged. Apparently, D told my friend that he only proposed because I talked him into it. He wasn't ready to move forward in our relationship, but I pushed him to take the next step. He also said things like the only reason we moved to a larger apartment and got a dog was because I wanted it. My friend couldn't believe he would say those things, especially since none of it is true! My fiance would be the first to say that he loves the life we have together and never felt pressured to do anything. 

The second time was when my FI and I hung out with B and D at a bar. B and I were going to the bathroom, so the guys had a few minutes of alone time. My fiance told me later that night that D was talking bad about me again! I am currently not working, and D said something to FI like, "At least my fiancee works. The last girl I dated who didn't, I dumped!" I don't know what the conversation was that led to this comment, and neither does FI since he was drunk at that point. I was shocked when he told me. It's one thing to talk bad about me to a friend, but now he's doing it to my own fiance!

I don't know what to do about this. B and D like to hang out together with groups of people, so it seems like I only see B when D is around. I'm not sure if she's aware of what he's saying, but part of me thinks she must be thinking the same things. I don't know how else D would come up with these ideas about me, since he doesn't know me that well. Should I talk to them about how hurt I am to know they talk bad about me? Should I just let it slide? I feel like it's driving a wedge between my friendship with B, which is something I don't want, especially with the wedding so close. 

@mrsbruff2b: I think he is feeling insecure about his relationship. I know B often compares their relationship to mine and FI's. I wish he wouldn't try to attack me to look better. At what point should I say something?