My personal guess is that while the stated goal of 'do whatever as long as it doesn't affect others' is good, our human biology will fail us in achieving this goal.

I already feel that humans aren't built for the world we made, that we can't handle societies as big and diffused as our current global culture. It breaks our capacity for cooperation and empathy by deliberately abusing the limits we have on caring for too many people or people far away.

Likewise, I think the end state of social progressiveness is going to butt up hard against core biological limits that will constantly try to push some of us towards bigotry due to outdated instincts that worked great when we were small tribes of monkeys, but are extremely destructive and unhelpful to modern human society.