Oppose a do-gooder law like Obamacare enough times, and you’ll pick up some new adjectives: evil, heartless, inhumane.

After all, if the president says he’s trying to help people, who are we to wonder if people will really be better off?

Obamacare is like the 2009 "stimulus" bill in this sense: Washington can't do something that big and not do some good for someone, somewhere. Of course, the opposite is also true.

But trying to quantify the good and the bad, both in the number of people affected and the help or harm done, is difficult. What one finds on the health-insurance market varies widely depending on one’s age, location, health, etc. Comparisons between insurance premiums today and under Obamacare don’t flatter the law. But it’s hard to tell how widely applicable they are.

For instance: The lowest “bronze” plan available to 25-year-old, nonsmoking men in metro Atlanta starting next week, according to new federal data, will cost $1,904 a year. They could find comparable coverage today as cheap as $794 a year, if they qualify for it.

Some men in that group don’t, and they’re almost certainly better off. But others surely do, and they’re set to see their rates more than double. If they make even $21,675, as roughly a third of 25-year-olds in Georgia do, Obamacare subsidies won’t offset enough of the increase to keep them from paying more than today.

Still, if these changes are unknowable, so are some others that don’t get discussed very often.

Take Bill, a 25-year-old nonsmoker in Roswell who makes $25,000 a year. Let’s say Bill is offered a new job that pays $30,000 a year. But it doesn’t come with health benefits, so he’ll still be on the exchange.

Before Obamacare (and with no deductions to itemize or credits to claim), Bill would pay about $1,400 more in state and federal taxes at his new job, a marginal tax rate of 28 percent. Oof.

But with Obamacare, Bill also has to consider how his health premium will change. At the lower salary, he gets $633 in subsidies. At the higher salary, he’ll lose every penny of that, ratcheting up his marginal tax rate to more than 41 percent. That’s more than “the rich” paid during the Clinton era.

If the job means more stress, longer hours, moving elsewhere or harder physical work, would Bill still take it?

He would. But we know some people wouldn’t, because this is how our income-based benefits have worked for decades. This has a negative impact, if an unquantifiable one, on the broader economy.

Now let’s think about another behavior we know to be similarly discouraged: marriage.

Statistics tell us overwhelmingly that the surest path to avoiding poverty is to finish high school, wait until age 20 to get married, and only then have children. What does Obamacare do to this path?

Imagine Jason, a 22-year-old who makes $22,000 a year. His job doesn’t offer insurance, but on the Obamacare exchange he can get a bronze plan for $566 a year, after subsidies.

Leigh Anne is a year younger, makes $18,000 and buys a bronze plan for $320 annually. Jason’s been dating her for a couple of years, and he’s thinking about proposing.

But first Jason checks the health exchange; he's heard there's some kind of "marriage penalty" for health insurance these days. And he's astonished to learn their combined health premium will be $2,003 a year more than they pay separately now.

It’s like a 5 percent pay cut, with nothing in return. Maybe they get married anyway, and keep moving on the path away from poverty. Maybe not.

We can find people whose lives will get better immediately once the exchanges open. They are seen.

But these future people making future choices — and history tells us they will be real — are harder to identify and quantify. In many cases, the amount of help they get from the law will never surpass the larger opportunities at a better life they pass up. The missed opportunities and forgone advances are, as the French economist Bastiat described them, what is unseen.

And the unseen explains why some of us don’t find it so evil, or heartless, or inhumane, to point out the real harm a supposedly helpful law will do.