If your other half says that it's because you don't love them enough you need to get a new partner who doesn't behave like a 10 year old.
You have to accommodate some disagreements in a relationship. Most men aren't going to disagree strongly enough on this one issue to use the nuclear option on the relationship.
Nice theory, but you don't want to marry someone who doesn't behave like a 10 year old, you want to marry the person you love.
The most important lesson I learned recently is how little impact logic actually has on real world discussions. Way too much of what we do is driven by emotion.
So, given that, instead of trying to use logic to sway someone who needs a ring, what are some tactics that appeal to emotion that can work?
The best you can hope for is a compromise.
- get a secondhand stone and have it re-set. - get certified non-conflict diamond (or in my case, an Australian diamond) - get some other precious stone
The best one is to get hold of a family heirloom. Costs nothing and has far greater emotional value.
If you refuse to buy a diamond, it's because you're cheap or don't love "her" enough. No amount of hand waving or sensible logic will make up for the fact that you'll just look like an asshole.
There's no logic in love, just shut up and buy her the damned ring.