One flaw with religion is that society expects everyone to follow a 'moral code' inherited from the ancients, in which the act of marriage is the only acceptable way to have sex. So, you can marry multiple times, get multiple divorces, marry underage, you can even beat your wife, just so long as you use the magic word MARRIAGE then you're fine and no-one is allowed to criticise you. But if you have a casual ('illicit') relationship, in some parts of the world you are to be deemed a criminal and should be locked up even though you have not hurt anyone at all.

This kind of situation shows clearly that it is necessary to renegotiate traditional ideas of morality to suit existing problems. Secular societies which have done this usually agree on one essential thing: what human laws must do is to prevent HARM from being done, not whether it is in accordance with some ancient system of 'morality' that everybody happens to accept because they are forbidden to negotiate it or change it - those who try to receive all kinds of insults and threats - even up to death threats.

But what if a society said, look it's none of our business who you have consensual sex with, as such, but what we are VERY concerned about is HARM being caused to others. So, we will make it illegal for sexual acts with those under a certain age to take place because the welfare of children under a certain age is damaged by sexual interference by older adults.

Taking 'harm' as the guiding force for lawmaking in the modern world, and setting aside 'traditional morality', will actually free us up to A) respect individual choices and preferences regardless of what we do or don't believe; B) address modern scenarios and problems; C) improve the essentially flawed nature of traditional moral codes which do not always prevent HARM from being done (in fact, they cause far more harm than they do good, in my view.)