What are they doing to the economy? Examples? Which crafts are they destroying? Which HNMs are they monopolizing for gil drops? You can't really give examples because the current system discourages transaction tracking. So, out of sight, out of mind right? If you can't demonstrate tangible effects of real money trading, it's a non-issue.
The truth of the matter, as I've said before, is that RMT activity is a sign of a healthy game. The lack of it in FFXIV speaks volumes. I've also said that some serious RMT activity would actually benefit our skewed economy by creating an abundance of crafting materials. With an influx of RMT, there would be a healthier crafting system with materials being much more accessible to everyone. The downside to that would be a more tightly controlled economy as in FFXI, where the parts of a recipe are usually more expensive than a finished NQ product. But that will happen anyway once enough players join and level crafts of their own. If I can purchase stack of meat mithkabobs for 2k each, I'd almost certainly say that's not to my detriment. If they don't mind making 100 gil profit from a craft, I don't begrudge them that. Woe to the rest of the crafting community that have a hard limit placed on how much they can inflate the economy - not.