What they don't have a right to do is deny employers the right to offer any terms they want. You're promoting authoritarian infringements on the right of consenting adults to engage in voluntary interactions.
If you were to invade Myanmar today, and impose a social democratic government that bans child labour, the result would be an increase in mortality.
Child labour only became unnecessary as a result of economic development increasing the average level of wealth in society.
Going back to the article, it's telling that you're trying to justify the authoritarian prohibition by comparing adults to children. Your ideology sees ordinary people as effectively children, and the state as their parent.
You're free to frame this argument in terms of individual rights or "economic competitiveness" or state paternalism. Unfortunately it amounts to little more than economic handwaving. At worst it's a disingenuous ploy to undermine the interests of the labour class, deluding workers into thinking you're giving them economic rights and freedoms ("you should be able to choose when you work!") when really you're just justifying your extraction of an even bigger share of their labour.
The common labourer has no economic power. The state, the firm, and (to a diminishing extent) unions do. I hate paternalistic states (and unions) as much as you do, but when you place no limit on firms' ability to extract labour from their workers, you end up in twisted situations where people are being paid sub-livable wages and expected to be on call 24 hours. Not because it's an economic "inevitability" (child labour inevitable? You seriously believe that?), but because it's the most amenable socioeconomic arrangement for the capitalist class.
I recommend you study a bit of economics.
Start with Adam Smith:
>It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest.
Then read this:
This isn't free market dogma. This is what 400 years+ of economic history shows us, and what any economist would confirm.
Wages and benefits improve as the wealth of society increases, and wealth increases as a part of the normal course of history, particularly when market institutions are strongly in place. Wage growth slowed as a result of the institution of economic-growth-destroying socialist laws and programs in the US and Europe.
And putting all of this aside, you have no moral right to violate another person's right to freely contract to increase your own wages. So even if economies didn't work as they do, such authoritarian prohibitions would be unjustiable.
That is what all the statistical evidence suggests.
Anecdotally, I've spent a fair bit of time in the developing world, and to me at least, it's obvious that the root source of the difference in working and living conditions between the developing world and the developed world is the comparatively lower levels of capital (tools, equipment, machinery, social capital, skills, knowledge) in the developing world.
And policing violations of other's right to their person or property, in prosecuting murder, and managing public property, in instituting and enforcing traffic rules, is absolutely a proper role for the government.
The role of government is not to avoid unnecessary pain. Government is a collectively formed institution given a set of powers to provide goods we cannot provide for ourselves individually. There is no objective reason why people, acting through their government, have a right to violate the rights of others, when clearly people have no such right when acting in the individual capacity. They do not have a right to make racist motives or hiring practices illegal, because it hurts their feelings.
And trivializing the harm done by racist hiring practices is disingenuous. Its not just 'hurting feelings'; its marginalizing citizens en masse.
Many practices, like slavery, that we now consider deeply immoral, were in place for thousands of years before the majority came to believe in their immorality. The fact that something has been done throughout history neither tells us it is moral, nor that it is immoral.
I think if you strip away the ideology (modern liberalism), the labels (government) and the appeals to convention ("this has been done for hundreds of years"), and look at the practice you are endorsing for what it is, it is clear that it is immoral.
You're saying that you and I have a right to threaten John with violence, because John won't hire Rhonda due to her race.
That is what all government mandates are based on: violence, and you want to use them to make actions that in no way violate another party's rights subject to violently enforced punishment, if they are based on a particular set of values, or refuse to help a particular party we want helped.
But most government most place most of the time its just social pressure. Fines for parking in the wrong place. A visit from a social worker. Lines painted on the highway.
Jumping from those to violence is disingenuous.
Something being the law doesn't negate its qualities. The law is enforced through the threat of violence. Ignoring this fact is euphemizing what your political ideology is actually endorsing. The fact that laws are enforced through the threat of violence is extremely important, because it tells us why a humane society does not use the law to punish consensual activity or noncompliance with morally illegitimate demands (e.g. the demand by income tax law on the population to surrender its private property and privacy rights).