That’s a result of all the easy credit for so long that caused the problems we’re in now. But he won’t listen to that. Again, as painful as this all is (and my heart does go out to you on this — so while I may sound dispassionate in my responses, it’s because I want to help, and not because I don’t empathize), I see it as a good sign. He is blaming you, which means at some level he knows you’re right — just not at a level where he can accept it. This is a form of denial, but at least it’s aimed at you.
This is a good time (okay, not so good a time) to ask the “Why?” questions. “I don’t understand. What did we do that has hurt your credit rating?” or, “Are they giving you reasons why your credit is bad?” or, “Did they give you a reason for turning you down?” Credit card companies won’t answer questions like that, but if he applies for loans at a local bank, he might get answers.
This brings up a thought, which may or may not be a good idea, so wait until you hear feedback from others on this before doing it. Suggest that if he’s having trouble getting credit, he may try to get a small business loan from a local bank — or get support for one from the SBA.
He’ll get turned down, of course, but it might be interesting to see what happens when official institutions tell him he can’t get credit because MLMs are not viable.