If you point out that he still has a while to go before he even starts earning money (I'm assuming he's still in med school and hasn't started residency yet) and that his student loans may likely be close to 7%, and show him the math, he might start singing a different tune if you point out given his current financial habits he would have to practice until 70.
I've been practicing less than a year, and although I discovered MMM a little bit before I graduated, I know that I need to achieve FI/ER simply because of my profession alone. Since I'm a dentist, I rely on my hands, eyesight, and fine motor skills. I am healthy and young, but as the years go by, I know that my eyesight will get worse, my hands will get shakier, I might develop some sort of back or neck pain from chronic work, or insurance companies will keep paying less and less, or malpractice insurance will skyrocket, or any number of possibilities that might drastically decrease my ability to earn an income. Not to mention that it's popular notion to treat doctors or health care professionals with disdain, mistrust, and outright hatred nowdays, and despite my love of people and genuine care for my patients, I know I don't want to deal with complainypants for the rest of my life.
Doctors can get some really good benefits towards loan repayment if they enter areas of public health - Indian Health Services, or the National Health Service Corps sites in particular. A lot of my classmates also decided to go into the air force - after 4 years of service, they are technically debt free. There are some options out there, but they are obviously not without sacrifices, and given that the average medical student in the US is accumulating $250-400,000.00 of debt at the moment, any help towards repaying loans should be considered.