Memes

This leaves out the horrors of the slave trade, both transatlantic and domestic.

That is an entirely separate point. Go read up on what the capitalist regime in Korea, that US installed, did rounding up, torturing, and forcing homeless people into work. These horrors are quite akin to the chattel slavery horrors in US.

Workers can leave. They can move companies, cities, states, or countries.

Except that's not how it works in practice. The baseline for the conditions that the companies offer is the conditions people experience when they don't have a job. In US, that means starving on the street. Therefore, job conditions only have to be preferable to that. Meanwhile, moving cities, states, or countries implies having the means to do so which people being exploited do not have. The fairly tale liberals tell about the workers having freedoms to choose better employment has no basis in reality. Nobody chooses to work in an Amazon fulfillment center and piss in a bottle.

Pays for the total upkeep of the slaves: Yeah, in the same way you keep up a piece of machinery. If it was no longer profitable to pay for the “upkeep” of an enslaved person because of age or disability, they were subject to being sold off for medical experiments, left in the woods to die, etc. Quality health care was not in the cards.

And that's precisely how things work under capitalism as well except the capitalist doesn't even have to worry about their worker dying on them because they just replace them. That's why Amazon lets people just drop dead on the floor as work carries on as usual.

If a slave gets sick it’s [the enslaver’s] problem: Only if it interfered with work.

The whole point of having slaves is so that they do work.

And if you’re making a comparison with modern capitalism, workplace injuries are very much the employer’s problem because of worker’s compensation. Likewise health care insurance is commonly employer provided. There are also pieces of the social safety net, with are partially paid for by businesses in various ways.

That's total bullshit, see Amazon example above for a counter point. In fact, there are countless horror stories of people being literally worked to death in US without being able to take sick days or seek medical help that they needed. And not just US, here's how capitalism is working in Japan.

Slaves come to work on their own: I see no downside to people having their own homes instead of whatever half-assed shack their enslaver provides.

The point you evidently missed is that capitalism reduces the costs for the business owner where worker is now responsible for ensuring they don't live on the street. Huge numbers of people in US are both employed and homeless. These people don't even get a shack. Here's an explanation for you of how this works:

Only has to pay for 8 hours of their lives: That other 16 hours was a hard won victory by unions. Going over 8 means paying overtime. Slaves didn’t get overtime, but they did get over 8 hours of work.

Most workers in US don't get any paid overtime. This isn't even restricted to blue collar labor. Unpaid overtime is standard practice for white collar jobs like software developers as well.

Your arguments aren't based on reality.