Same reaction. I've anecdotally asked this same question: "man-made or natural diamonds?" to my friends in the past – mostly because I can't get past the ethical concerns, but wanted to understand the other side.

I found majority of my men friends argued it's the same diamond without the ethical concerns if you go man-made, while majority of my women friends chose natural (reasons included social pressure, the story, and so on).

Anecdotes aren't proof. But perhaps there is something to looking at this from a gendered (proxy for giving vs. receiving?) lens.