Political Memes

Credit scores are opaque ratings of people kept by private organisations

They are only opaque to the extent that reduces the ability to game them. It's very common knowledge what the primary factors are that determine your credit score:

1. payment history (it makes perfect sense that seen as more risky to lend to, if you don't make your loan/credit card payments on time). Also, the more consistently you make your payments on time, the more credit limit increases you get, which helps with—
2. utilization (it makes perfect sense that you're seen as more risky to lend to, the closer to 'maxed out' you commonly are)
3. derogatory marks (e.g. being sent to collections, having your house foreclosed on, etc.; makes perfect sense for things like these to be considered evidence of you being risky to lend to)

Without paying a cent of interest, my credit score is in the 800s, simply because I use my credit card for everyday purchases, then pay off the statement balance each month, and have done this consistently.

used to refuse business to people effectively based on their spending & borrowing behaviour

"Refuse business" is deceptively overbroad—no entity will prevent you from fully paying for something in cash based on your credit score, for example. But they may refuse to lend to you, if you have a history of failing to repay money that was lent to you in the past.

There's nothing shady about that, it makes perfect sense for one to be less willing to lend money to someone who has a reputation of not repaying their debts.

Without a credit score or similar system, lenders either will:

1. treat everyone with the same caution as they would someone who's never borrowed anything before (which is detrimental to people who reliably repay their debts), if they're ethical
2. guess at creditworthiness based on prejudices/biases/stereotypes of the immutable characteristics of the individual looking to borrow, inviting bigotry to play a major role in who gets loans, etc.

Credit scores are purely beneficial to good/reliable borrowers—it seems that invariably, those who have the biggest problem with them are unreliable borrowers who really wish they could hide the fact that they don't repay their debts from the next entity they intend to get more 'free money' from.