He does have a point and I find it curious that as an adult yourself why you can't see that. Unless they're aiming for a career that obviously holds math to a high degree like engineering, then quite frankly I wouldn't hold it against them if they didn't care anything farther than comprehending basic math starting with Calculus.
Few years ago, I look at my relatives for help with math who are doing well on their own (one is a senior accountant and another is a salon manager), yet they couldn't competently help me with math since they didn't understand anything past algebra and some basic Calc work involving derivatives since it decades that they even touched upon the subject.
We're basically taught lots of useless shit, yet get told that we absolutely need them for some reason later in our lives when that's entirely dependent on what you're going to do. I'm more disappointed people don't point out that being able to comprehend and do well in these "useless" classes will build your own discipline in getting things done right, rather than saying along the lines that the information will actually be useful in any way. You mind as well tell anyone in the business of mechanics, private contractors, etc. that they're still teenagers if they didn't care much for advance math.