Never... boundaries work both ways, and you don't have to quote "keep your mouth shut".
The interactions with your husband's ex girlfriend sound very inappropriate to me.
I think probably one of the biggest factors of healing from a WS side is having strong boundaries, and enforcing them. It's okay to enforce your boundaries with your husband. It is up to you what the consequences are if he breaks those boundaries.
The fact that he is undecided on R or D does not give him a license to do whatever he wants.
Are you in MC? If so, this would be a good topic to bring up.