It's related to how Lenin used the term social chauvinist, which were nominally socialist parties who nevertheless supported their nation in WW1 rather than adopting revolutionary defeatism. So social fascist is a derogatory term for social democrats or self-identified socialists who espouse imperialist ideology.
What do you mean by the Social Fascist term? Is this an inside joke I do not get?
It's related to how Lenin used the term social chauvinist, which were nominally socialist parties who nevertheless supported their nation in WW1 rather than adopting revolutionary defeatism. So social fascist is a derogatory term for social democrats or self-identified socialists who espouse imperialist ideology.