There is really no point in debating Old Dad on the merits of his debt-free absolutism. He's promoting the Dave Ramsey plan. Dave Ramsey is a personal finance guru who targets Evangelical Christians with his biblical financial advice. He teaches things such as the "debt-snowball method" in which people pay off smaller balances first instead of their debt with the highest interest rate because he assumes that his audience is too stupid and lacking in motivation to stick with a plan that takes longer to see results, but saves them money in the long run. He may be right with regard to his assessment of his target audience, but his methods really have no place in a discussion about what to teach highly gifted children who are capable of understanding more complex financial strategies.

https://en.wikipedia.org/wiki/Dave_Ramsey
https://en.wikipedia.org/wiki/Debt-snowball_method