Subjugated people are the center of liberal activism and thus will play a bigger role. It's the same reason why minorities are more left leaning than whitesand why?
You can never "move forward" in a socio-cultural sense if morality is subjective as your post indicates.left is right and right is wrong. Society progresses and it doesn't stay the same. Modern conservatives and fundamentalist's Islamists would be considered liberal heathens during the caliphate and the renaissance in Europe. People just need to wake up and not romanticize the past when people in the past themselves were romanticizing another past. Lets move forward.