The surface text is that MIT students are better positioned to succeed at YC than people from more pedestrian socio-economic backgrounds. Altman isn't directly recruiting at community college students for reasonable reasons [by which I am not saying that there aren't potential founders among community college students, but that it is easier to optimize on eliminating false positives among MIT students than among students at less selective institutions]. You're on your own for the hermeneutics.
If you are trying to recruit the best of the best, it makes sense to recruit there. But you will have stiff competition from everyone else seeking the same. You're probably also looking at CalTech, Stanford, Berkeley, and Princeton with the same eyeball. And sama is saying that some of those companies that set out to recruit the very best and most prestigious graduates are not always the very best companies to work for. That's it. If you graduate from MIT, you don't have to work for Apple, Google, Facebook, or any other company that anyone has actually heard of.
I came from the middle of the bell curve, and my first job was working for a start-up. I didn't need sama's advice, because I was just looking for the first thing I could find, rather than the first thing that would not spoil the purity of my perfect, pre-planned resume. That's why he was aiming at those busy beavers in Boston. He's just saying that people might be happier if they chased after the rainbow unicorn farts rather than prestige.
I have worked closely with graduates of Alabama, Auburn, and Alabama A&M, including the smaller satellite campuses. Those are not "cow colleges". Their graduates are not bumpkins. They are overly religious and entirely too enthusiastic about football, in my opinion, but they still know how to do the work. They also know how to chase their dreams, even when afforded fewer opportunities to do so.
Recognize that "bumpkin" and "cow college" are derogatory or dismissive terms, you may have used them without thinking about why you shouldn't, and that you may need to reflect on that a bit.
There are highly capable graduates from community colleges, e.g. Hanselman. But investing is about maximizing the odds with finite time to collect information. Altman is chasing the odds by taking his dog and pony to Cambridge, Mass rather than Troy, Al. It's business.
I apologize for offending you. The reference was self-depreciating on one level and an obscure reference to a respected tech leader that Altman's recruiting optimization tactic would miss. I'll point out that your stereotyping is 'Alabama bumpkin' by value rather than reference.