I feel as a parent I have the right to and should check the social media that my DD 12 is using. DD does not mind and will happily show me the sites she uses and shows me who she is following and who is following her etc.
A while ago she showed me something that DSS 12 was posting, I did not think it entirely appropriate. I told DH about it, he went nuts saying that I had violated her and DSS privacy by looking at what they were doing on line. If she was following him she had no right to show me. I disagreed, but did ask DD not to follow DSS or communicate with him online any more.
Am I being unreasonable, I think I am being a responsible parent and trying to keep my kids safe. I did not expect the response I got from DH.