It sounds like you are having typical issues when in a blended family. The issue may be not as black and white as you think and that may be causing this problem. It is helpful to give your adult children boundaries that respect everyone's opinion. Try to develop rules in your mind that would respect your boundaries and give them a chance to still verbalize their opinion. Decide where when and how their opinion can be considered and verbalize this to them and to your husband. When you establish when you are open to their opinion then you will find that you welcome what they have say. When they begin to behave within those rules then they will have a say. When you and your husband can agree on the circumstances then you have a way to lay out your expectations. Think of this problem in terms of what can be done to hear them but not feel violated.
I feel that my husband treats his children as adults in terms of their opinion and as children in terms of their needs. The little adopted child is completely ignored in terms of her needs