It's hard to pin down a firm definition of social justice, but here's mine: you are given stuff based on your membership in a social group rather than your individual deserts. Hard to deny that the Democrats are the party of that.
What is hard to undertstand why enterprising people such as the Asian immigrants are down with that.
Let us not forget that the Democrats were the part of segregation, Jim Crow, and slavery. Republicans freed the slaves, desegrated the schools (Eisenhower and Nixon) and voted for the Civil Rights act in larger numbers than the Democrats.
But the Democrats figured out that they could buy minority votes by giving them stuff robbed from Republicans.