Whether you agree or disagree, I believe that the people who consider some SJWs to be “regressive” is that the system used to be that social conservatives used to tell people what to think, we had a period of open-minded exploration, and now SJWs are advocating moving back towards a system that people are told what to think, except it’s social liberals who are doing the telling. In the sense of someone telling people what to think versus a embracing a wide range of different views, it could reasonably called regressive — perhaps up one level of abstraction if you want to get technical.

Note that I am not supporting one view or another, rather I am just explaining how the term can be used to reflect one’s perspective accurately.