The point is not about who you should or should not respect. The point is that other people are going to respect certain aspects in people that you don't agree with, and it's silly to say that respect is not real just because you don't agree with its motivations. It's the same reason we don't like c# developers who say that python devs aren't real programmers.
And to drive the point home: those diamonds you see in rings have a non-negligible chance of coming from child slaves, who have been torn from their families in civil war and will probably be setting off land mines once the diamond mines run out. I actively disrespect the choice to purchase them.