It wasn’t slave labor, exactly, but it was massively exploited labor. 75 years ago China was easily the poorest country in the world and it’s people were living in the equivalent of $1/day, possibly less.
However, the entire goal of the socialist program was to alleviate that poverty and exploitation, not by enslaving people but by developing the country’s economic and industrial base.
Today, Chinese people have a higher average purchasing power than US citizens do. That means the average Chinese family can afford to buy more goods and services than the average American family. Wealth inequality is also way lower in China than in the US which means that way more of Chinese people have better purchasing power than USians do, simply because that’s how averages work. The US raises the average by making very few people very wealthy and China raises the average by making their billion residents sustainably and incrementally more wealthy.
As for slave labor, the US imprisons more of its people than any other nation on the planet and all of those prisoners are subject to slave labor and massive debt burdens. Official US slave labor from prisons produces over $11Bn in goods and services, much of which goes to the profits of for-profit prison management companies.
China has no such system.
It’s a farce.
There are never only two choices. It is impossible to actually construct a real world situation where in there are only two choices. Even in an elementary school, given a test with only on question on it and it only has two answers, you can eat the test, scribble on it, punch the computer screen, walk out, etc.
Even in prison with guards pointing guns at you and putting you in a position to do either A or B you have options.
However, the concept of lesser evil is a shallow abstraction of the real world experience of pragmatism. Amongst all of your options, what course of action leads to the most desirable outcomes?
This is a real thing. We do it all the time. People in positions of grave responsibility have to do it with consequences and constraints that are absolutely gutting. Let’s say the war has already started, well, now you have to make decisions about how to avoid losing the most strategically important objectives, even if that means people dying. In fact, the strategies employed in war force decision makers into these sorts of choices as a matter of course - an opponent knows you don’t want to make certain sacrifices and will therefore create pressures that trade off those sacrifices with strategic objectives. Sometimes it’s not even that they believe you’ll give up the strategic objectives but the delay you have when choosing will give them an advantage, or the emotional and psychological toll of being put in such situations repeatedly over a long campaign can create substantial advantages.
Lesser evil is rhetorical sophistry or mildly useful thought experiments when exploring the consequences of ethical frameworks in academia.