That argument (repeated in other words by several posters) is entirely circular. It's fair because society has said it's fair.
It's not just a case of someone randomly deciding that it is fair that women are not discriminated in the work place just for being women. The fact you think it is fair says more about you that the rest of society!
Do you agree for example that TWAW with all that entails, because 'societal values and norms' have decided they are?
This isn't really a comparable argument.
How's this for a thought exercise, imagine you came to a country where the law wasn't such that people could take 6-12 months off to have a baby and be guaranteed of their previous position if and when they returned. How would you convince the lawmakers to enact this law?
I have actually done something like this. I'm a university academic and I teach career development . I have a specific interest in women's career development.
I organise student debates and one year the topic was enhanced maternity leave....they were asked to either argue for or against. They weren't allowed to just shout 'its not fair'! They had to provide evidence ( as did those in the 'for' camp).
The students found that there is a lot of evidence that enhanced maternity leave is a good thing. A PP has outlined some of that evidence but from a business perspective it is clear that enhanced benefits ( be that maternity leave, parental leave, Annual leave, flexible working etc) mean that employees feel valued and this translates into higher productivity and less staff turnover as employees are more likely to stick around. This often offsets the costs associated with maternity leave.
You'd be explaining how beneficial it would be to woman to not have to make the choice between a career or a family, and how companies would benefit from showing loyalty to their employees
There is evidence to show this. I'm not sure why you present it like it's a bad thing!
But then a small business owner challenges you: Hang on a minute. While it's true that it might be worth it for me to retain specific employees, it certainly wouldn't be the case for every single employee. Obviously with some it would be far more hassle and cost to keep the position vacant rather than find new permanent employees. So why should I be obligated to support the life choices of any random employee?
How do you reply in way that would satisfy that business owner?
Because that is part and parcel of running a business. If you don't understand that, then you shouldn't be running a business. It's really as simple as that.
It might help if you actually viewed your employees as people who have lives outside of work.