I have to agree with CW... something is amis. There is something unspokan there. I first thought it was something that may have happened between your hub and your SIL but CW brings up some good points. Your hub must have some reason other than a gut feeling to be so vehement about someone, anyone, regardless of who it is. Most times, a gut feeling about someone just puts us on guard not outright hostile.

Tough call. It depends on how involved you want to be with your brother. At the end of the day, your relationship with him is ultimately the one to suffer or grow. Just as you are kind of a package deal with your hub, so is he with his wife. Not that you cant have one without the other but the person closest to us (usually our spouse) has the most effect on us for whatever reason. Could get right down to you just get tired of hearing your hubby talk negatively about her so you just avoid her altogether in a round about way, not spending time with your brother. If that can make sense.

I guess it depends on how far your willing to push it. Pushing the subject with your husband could cause a major meltdown or could resolve an issue. Talking more in depth with your SIL could give you some insight or make her shut down like fort knox. You have to decide what your willing to risk.