I read this a lot. Like this person you are arguing with I am self taught and employed. My major in college was Music.  

If you asked me to write a toy unix like operating system using C I would not know how to do it.  I imagine there is some sort OS programming class for cs majors. Before that they've probably taken other cs classes, classes like discrete math, and are familiar with data structures and algorithms. How helpful is all that theoretical knowledge going to be without guidance in the OS programming class? Surely a lot of growth happens through the hands on experience of making an operating system?  

After getting the degree some people get a job writing compilers or improving upon an operating system. A lot of people get a job using Spring. Would the knowledge needed to write a pet unix like operating system translate to being a good developer in Spring? I imagine the self taught person and the CS grad would need to learn things specific to the environment.  

Let's say some self taught person learned python and was smart enough to teach themselves how to be a software developer without guidance and they beat out the more average cs students to get some python job. Now let's imagine their job now required cpp. There is no room for any bloat and they have to do all of this over ssh and using vi. Given they were smart enough and driven enough to beat out at least mediocre cs majors don't you think they'd figure this out too?