It's also the freedom to make zero changes to the free code you were given, reuse it in your closed source software, and pass it off as your own.
In a way, I feel like I should be a big enough person to be okay with this, but I'm not. The possibility bothers me.
No, the MIT license requires attribution by including the original copyright notice with any distribution of the software. You can claim credit for the parts you build around it, but you can't claim to have written the MIT-licensed part.
One of the distinctions I like to draw strongly is between "nice" and "good". They are not the same, and at times, are actively at odds with each other.
It is certainly nice to give away your software to everybody, unconditionally, and not be bothered if your code does happen to end up being a fundamental component of some multi-billion-dollar company that gives you nothing.
But I'm less convinced that's necessarily good. In a world where you must live under the assumption there are bad actors, I think it's OK to put into your license that they can't necessarily do that. It is good to prevent the exploitation of anybody, and that goodness extends to preventing the exploitation of yourself, even if you also clearly have direct personal interests of your own.
I don't think "being comfortable with being exploited" is a component of "being a big person".
On the other hand, we often bring to mind mental examples of software where we slaved away for years and years to bring some unique new product to the world, only for it to be stolen by the big bad corporation for no compensation. My verbiage above about "exploitation" probably brought that to the reader's mind as the topic of discussion. If that happens, yeah, it's bad. On the other hand, that's not really the dominant case for software. There's a lot of open source put out there that's just a few day's work, which is still plenty valuable at scale, but if someone took one of these little things and incorporated it into their product, it's not really that big a deal.
I have several such small little things and they're all BSD. If a big corporation did somehow walk off with one of them, I'd legitimately be flattered, because I know that while it may have saved them a bit of time, it certainly isn't a core component of their product and had they needed to implement something themselves it would have been a trivial fraction of their time. I know I can say I'd be flattered because to some small extent, this really has happened, and I really was flattered and appreciative, so I'm not just hypothesizing about my future emotional states. I'm well aware on all levels that my ~two weeks total effort on the project in question, which I mostly did for my own purposes and for which the open source effort was essentially a bonus, doesn't entitle me to significant compensation for a product whose size is measured in person-decades.
In the context of the types of projects I was imagining, a company would likely just rewrite any code that wasn't available via MIT or similar. If I'm not getting anything in return either way, am I being exploited?
Logically, if the outcome is the same for me, there's no reason to make others redo work.
But as rare as it may be, there have been many cases where an open source code base really was "exploited" by any reasonable sense of the term, with corporations slapping their logos on it and reselling significant works in violation of the license, and those cases are significant because of their size, even if they are rare.
As a simplified example, consider Corporation G and Corporation P. One will eventually lose market share to the other, go bankrupt, and be replaced by Corporation R that bases its business practices on the more successful one (then the cycle repeats).
Both are evil, as corporations are wont to be, and in particular will never release anything under a less restrictive licence than they have to (so they will never release software under a MIT licence). However, G will release software under the GPL if this allows it to save work, whereas P will always release software under a proprietary licence, even if this forces it to expend more resources rewriting GPL functionality.
Releasing code under the GPL exerts a selection effect that favors G over P, and in the long run results in corporations that release somewhat more software period - and significantly more software under FOSS licences - than if P was not forced to redo work.
Yes, because of the GPL, they have to give RHEL customers the source to all their patches, but what difference does this make in practice?
they have to give RHEL customers the source to all their patches, and allow them to share it with the entire world.
In practice, that means everyone gets better software, and RedHat gets compensation for their hard work.
CentOS is the difference; it is one of the most widely used distributions has the same stability and longevity characteristics and gets security fixes just as fast as RHEL.