How to unpublish story application ?

Hello,
I'm using EasySocial in a way users can't post directly in the stream. What only is streamed is badges and some others stream from another ap.

If I remember correctly, in previous version I could unpublish in backend application "Story". So when user tried to post text in the stream it didn't function. (Then I hide the stream entry with css).

But now when I try to unpublish "Story" in application I got this : "You are not allowed to unpublish core applications"

Is it due to the last version ? How can I still remove Story application ?

Thanks a lot for your help,

Edgar