Snowball.....
Pay off the lowest balance and add that to the next highest once paid off.
Continue until you have paid off all debts.
It is not dumb, what he is doing is teaching you how to get ahead of the game. Most are in serious debt with credit cards, behind in their payments on everything and he shows a way to get out of the ditch and get caught up.
The interst rates do not matter because if you work his plan you will pay them off long before you would making minimum or no payments at all.
You need to know his entire plan, not just parts of it to understand where he is coming from.
You start out by putting $1000 in an account he calls the emergency fund. This will give you something to fall back on when something goes wrong. This is not to be touched. The goal in the end is to have 3-6 months of your expenses set aside in this same fund, again to never be touched except for an emergency.
You then create a 0 based budget where you spend every dollar you make on paper before the month begins. You have to give every dollar a name and stick to the budget. you would be surprised how much money you can save just by doing this. Money seems to fly out the window without a 0 based budget.
You then can start on your credit cards, if you have them or any other debt, car, boat, whatever. Smallest to largest in terms of what you owe on them. You take any extra you have and put towards the smallest debt and pay minimum on all others. Once the first one is paid off you add it to the next largest and continue minimum on all others. Do this over and and over until you have debts paid off.
Once you have everything but the house paid for you can then start to expand your savings and extend your emergency fund to reach the 3-6 months expenses.
When you do pay off your house - FREEDOM! Then you can truly start to save and live like noone else as Dave likes to say.
15% should go to savings and you can fund for your kids college or whatever if you don't have children.
He doesn't even preach against not buying stuff, just to do it with cash. You want a Corvette, fine, when you can pay cash for it have at it.
How can this plan be dumb or a scam? It works and he has helped no telling how many people get out of debt.