Although I am kind of miffed by the last sentence, I admit I'm one of the people who programmed WAY before college but in my experience most CS majors who didn't simply didn't choose to do so, as opposed to having lacked the opportunity to do so; you're dismissing the thousands of hours spent coding as a child (more than most CS majors invest in programming during college...) without the internet or anyone to teach me anything as "opportunity"
I have an issue with someone dismissing thousands of hours of invested effort as "having an opportunity". And the same is of course true for someone who went to the library and learned first year math.
I would gladly hand over some C code to someone who's really interested in programming, but has only ever written python. I can't say the same about someone who's only known Java. So experience with C, isn't really a good bar to judge programmers by, not by itself anyways. You don't need to know how the stack works for most issues in C, and after you can make you stuff compile, without asking questions, is the time to learn about compiler flags.
So if that's the only argument for using an obscure/broken version of C, then it's a crap argument. If you've been doing CTF for years, the school needs to offer you CBE, not force you into a class where you'll only break the curve, and still be bored.
Also, I'd gladly turn away women and minorities both. If you're handed a problem you know has a solution, and you give up because it's hard. Your skin color or sex is irrelevant, if you're the type that gives up when it's hard; you're worthless as a programmer. (But that might just be my obsessive need to solve any problem I don't understand, so I might not be the best judge)
The problem with c is that the advanced things get in the way of the basics. You get students asking why their if statements didn't work and to answer you need to teach them GDB and valgrind and different compiler flags and how the stack works. This is a recipe for students that don't end up learning either thing. And it slows everything down so in the end of the year you can't cover everything properly and end up with mediocre C programmers you would never trust near a real C codebase
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Another thing to remember is that we should be very careful about that drill sergeant mentality that intro to CS should be hard and painful. This advantages students that had the opportunity to program before university and often ends up turning away women and other minorities from the field