You are absolutely correct in that embarrassing family members is completely prohibited. There is no heter in Halacha to do so. And if asked, these unschooled thoughtless organizers and protesters never halachicly justify what they’re doing to third-party family members because they have no explanation or even understanding.
If you look at any of these cases there’s virtually never any siruv against the family members.
And that’s all putting aside whether they’re even correct about the husband himself, altogether.