OP: I have not found any source online that the rule has changed. If it has, please share proof.
This has nothing to do with Delta. Every airline has turned people away because of this rule. This is why I put it in big bold letters on the DDF South Africa wiki.
If you get turned away by South African immigration for lack of the correct paperwork, guess who is on the hook to fly you back home? That's right, Delta.
Which is why the airline is often stricter than the immigration officials (in any country). That the individual agent you saw that didn't check your documents is in no way indicative of the actual rules.
I'm sorry you had this experience. I'm sure it sucked, and I don't blame you for not wanting to step foot on another Delta plane. But please do not blame antisemitism for a bad customer service experience. You're doing the rest of us a huge disservice.