Blood diamonds are terrible, but the overwhelming majority of diamonds produced these days are not blood diamonds relying on slave labor, they're mass-mined products relying on colossal-scale industrial machinery. That's why Russia is #1 and Canada is #3 in worldwide diamond production today: even the world's largest diamond mines have 1-3k employees vs. massive production.

That's not to paper over the issues with the industry (environmental, poor working conditions, poor pay etc) - but those are more generally applied to any mined product. I'd be willing to bet that your average set of modern electronics cause far more suffering than your average diamond: see conflict resources such as tantalum, tin, tungsten, gold.