The classically liberal approach to social issues was to challenge traditional conservative beliefs: Christians good, non-Christians bad; men strong, women weak; straight good, gay bad, etc. Liberalism (again, in the classic sense) says these group identities have no place in the public sphere, and should be given no legal recognition. A citizens is a citizen is a citizen. A woman has every right that a man has, a gay person has every right a straight person has, etc. That's why it was liberalism that fought the racist and sexist behaviours that were normal in decades past. 

But the left is no longer motivated by liberalism. Instead, they've turned to cultural Marxism. Under that model, it's groups that matter, not individuals. We shouldn't ignore that someone is a woman, or Asian, or Catholic, or Muslim. Those identities should actually be our main social role, and balancing the outcomes of those groups the goal of justice.

Very different ways of looking at the world.