The reason stores like The Bone Room do not have personal or demographic information on the remains they sell is because medical cadavers are anonymized. The Bone Room respects that, even in cases where they have purchased bones with a known provenance, and the topic is extremely complex. In short however, this means that the morality of the remains being sold is almost entirely dependent on the reputability of the person selling the remains, and retailers are comprehensively vetted and monitored because of this (there are obviously exceptions, but they are immensely rare).

It is extremely rare for educational remains to be initially sold as parts (though there are of course examples where it did happen). In the wild and vast majority of cases, an individual bone is the result of donated remains being reduced over time through repeated dissections to the point that only the bones are left. Because of this, it is safe to say that medical cadavers are the most exhaustively inspected remains on the planet, and signs of foul play would undoubtedly be noticed (there are quite a few examples of this).

China and India were the sources of most modern medical remains, though both countries have stopped the export of human remains. While yes, I cannot deny that there were instances where questionable methods were used to obtain the remains (the term is 'anatomy murder'), I only know of two specific examples off the top of my head. The first is the Burke/Hare murders, which were committed during the early 1800s, and the second is the very famous Body Worlds exhibit (and hoo boy is that horrifying). Both of these were the impetus for sweeping global legislation to prevent similar situations, and Body Worlds is the primary reason China stopped exporting medical cadavers (because, and I am being uncharitable, it is hard to credibly deny your crimes against political prisoners when you ship the bodies of said prisoners to western countries with bullet holes in their skulls).

Aside from cadavers sourced from india and china (which again are no longer allowing the export of educational corpses), the remaining remains on the market come from legitimate pre-mortis consent given by the former owner of the parts in question. There are many, many examples of this - leaving your body to medicine/science is quite common in the US, and is an absolutely vital part of our medical infrastructure, and is generally considered a very noble choice to make. It is important to explain here that medical cadavers in the US are shown a degree of respect that can quite accurately be described as veneration, and disrespect of donated remains is emphatically not tolerated. And while US-sourced medical remains are rare to see sold outside of a medical context (US law is extremely strict on this matter), it does happen. I urge you to consider why you think this would not happen in other cultures, or why they would not have similar attitudes towards body donation and donated bodies.

A specific example of a non-western attitude towards funeral practices (and oh boy is that a complex topic) would be memorial Japmala beads - a Nepalese tradition whereby Japmala (kinda like a rosary but for asian-originating religions) are made from bones donated to the temple by a (usually devout) person and are thence sold to raise funds. While done with consent, remains sourced from this practice are not infrequently sold for medical use on the condition that when the bodies are reduced to bones, they be returned to the temple. If some are removed, or missing (say, because they are a good example of some condition), or they were destroyed as part of their work, this isn't objectionable - so long as the remains are treated with respect, it's seen as benefiting the community as a whole.

This does not specifically translate in this case, but I've included it as an example of ethical sourcing of remains that really does not gel with traditional western views on the subject.

I can imagine a great many awful things, but that does not mean they are happening. This specific argument has really irritated me, in a way that I strongly suspect is unfair.

Mythbusters began almost a quarter century ago, and has had an outsized impact on science literacy and education. I think it's unfair to characterize this as mere passing entertainment for the global 1% (and additionally it totally ignores the US' cultural hegemony). Although certainly not a traditional use of human remains, the fact that we are still having a discussion about the topic twenty years later as a result of the episode could easily be argued to be a sign of the great impact the show has had on culture in general and thus tautologically justifies its own existence.