Interestingly on the diamond aspect of things, DeBeers became associated with price control and cartel images instead of respected as a design house. FWIW, DeBeers pioneered cutting and some of the artistry we associate with jewelry today. Sure, they also price controlled when they were allowed, but so do fashion houses with their twice yearly price increases.
And as for judging those who wear clear, sparkly stones, keep in mind that anyone reading a mass produced magazine (generally speaking, anything over a million copies) or insert is participating in the diamond trade. Most of those pieces are printed via gravure, which uses diamond heads to engrave the printing cylinders. Yes, they use industrial grade diamonds, but that's what the majority of diamond mining is for anyway (industrial purposes). No, diamonds aren't rare, but gem-grade diamonds are comparatively rare.
Again, my main point is that while we all make judgements based on what someone wears or how they present themselves, we are easily fooled into thinking that WE don't contribute to X, Y or Z problem. But we do. Chances are very good that if you live in the US or above the middle class anywhere in the world, you contribute fairly directly to almost everything you think you stand against.