Societies are fluid.
Animals as well. Otters were once monogamous. Very moral, middle class and proper. Hunted to near extinction they are now a swimming pack of immoral hippies. Changes in economy, crops, science -- All these influence.
Changes in overall situation often require changes in ethics, morals, laws, attitudes, etc.
Those attempting to adapt to the new situation will always meet resistance from those who believe the old, outmoded answers should be used regardless of the situation.
There has been a lot of talk in this thread about rights.
So far as I am concerned only two rights are needed.
The right to agree to the relationship you choose to be involved in -- Regardless of what that relationship might be.
The right to walk away from that relationship if, or when, you decide that relationship is not, was not, or is no longer, right for you.
Those two rights give you the right to
Decide
Change
Develop
Admit you made a mistake
Move on.
And those are all the rights a person needs to become a full human being.