The UN should absolutely draft resolutions that expressly forbid loan discrimination. Why? Because it is, in fact, discrimination. And regardless of how you cut it economic discrimination is a hard thing to overcome and a draconian thing to do. I think the UN should take the necessary steps here and do the right thing.
Due to the increasing gap between the rich and poor, the United Nations should forbid loan discrimination and impose fines and penalties. Loan discrimination prevents all equally qualified candidates from receiving resources that can improve their community or their life. Loan discrimination makes it difficult to improve society in other ways, particularly when preference is shown to a certain type of group or business.
I don't think the UN has the ability to enforce a resolution like this, I also don't think it's the job of the United Nations to be telling businesses who they can loan money to, I think the United Nations should be used for other purposes that they could reasonably achieve.
The United Nations should not draft resolutions that forbid discrimination. Furthermore, they should not subject discriminating practitioners to heavy fines. Globally speaking, if a small poor country should try to take out a loan, and the larger more wealthy country knows that said small country cannot pay it back, this could lead to predatory loaning. While it could lead to political hissy fits among trading countries, very little malicious action would be taken from being denied a loan. Having the option to discriminate loans keeps all countries safe.
For the United Nations to get involved in resolutions like that would be the equivalent of a boss trying to micromanage everything an employee does. It's just not needed, and it wouldn't be worth the time or effort to do. Loans and the financial markets are very fickle and subjective in every country.