I've been trying to get a handle on this one. It started showing up on my facebook via my brother's incessant sharing of Progressive/Liberal/Academia/Left Theological memes.
My question is: "How is this different from ye old solidarity?"
The answer I've arrived at thus far is that identity politics shattered solidarity by focusing on individualism, and inter-sectionalism is the result of trying to band-aid it back together with an intellectual bent.
Haven't gotten farther than that, though.