You’re not wrong, but the prior comment references “morale issues” which is different from “moral issues” or morality in general. The former is about the troops feeling of well-being and optimism (morale) and the latter is about ethics and right vs wrong (morality).

At 0% interest the cost of your money is nothing, so you save nothing by paying it off early. you will be better off taking your extra money and putting it towards other debts (1st) or investing them (2nd). In fact, even if you do nothing with you extra money now you will still come out ahead because of the future value of the dollar decreasing with inflation.