I think it's perfectly fine to expect users to understand the terms. They downloaded a piece of code for free from a website with no company or support programme other than "hey I hope this is helpful, if you run into any issues I might be able to help over email". If it turns out that the author can't or won't help, accept your loss and fix it yourself, pay someone to fix it for you or wait for another volunteer to fix it.
Alternatively, they bought some kind of product that included the code. If this product breaks, they must go to the company that makes the product, not the author of some library it uses. It's not like you're going to expect some sparkplug manufacturer to come up with a fix for your car when it breaks down, do you?
People who feel entitled to anything when they get something for free are selfish assholes and should not be defended. They know fully well that they don't have any right for support, but they will make demands regardless, hoping that the other party will break and give in.
I agree that you need to have a plan for people like this, but in most cases, that plan is "I'll just drop the project if it becomes too much of a hassle". And in my opinion, that's a fine plan.
If I'm a baker and sell you a loaf of my bread, I don't expect folks to email me complaining their welsh rarebit didn't come out right from the grill. Learn to cook or, in this perhaps strained analogy, learn to program and then come back and ask a more intelligent question.
> rage quit
And there we go, the automatic assumption that because an author has basically had enough of ignorant twats you paint their actions with these lazy characterisations. I don't think this author rage quit, he's just had enough of people with "contrarian" opinions such as yours. A license !== user entitlement.
But here's a contrarian view - I'm not sure why someone offering a project for free in the educational space would expect users to act like paid professional customers. Or expect them to be non-noob experts who can modify and build the project without hand-holding.
Or assume that email would be a viable line of support for a project with literally tens (hundreds?) of thousands of users.
Or even expect them to be adults.
So while I sympathise with the rage quit, I don't think it's realistic to release code and just expect users to understand - never mind accept - the terms you set for its use.
All open source projects comes with politics included. You have to have an understanding of the space you're working in, the kinds of users who inhabit it, and the kinds of relationships they're likely to have with them.
You need to know what your support boundaries and support technologies are. And if you work in a space where some of your users are likely to be assholes, you need to have a plan for that - even if it's just knowing that it's fine to ignore them.
Edit: to be clear, I think this is more of a general open licence problem than the failing of this one specific author. Open licences don't encourage authors to define boundaries, or even to understand that boundaries are necessary and terms need to be defined. So it's not quite a surprise that things like this happen.