Reciprocate when they want to read the changes you made, if their heads don't explode first.
Which is sad, because it's not rocket science.
PS: You should have yelled back "We have an illiterate guide here!" Anyone berating reasonable behavior deserves to be called out as an asshole.
In general the likelihood that the parties have read the contract doesn't have any bearing on the enforceability of it. But most such contracts are also contracts of adhesion (roughly speaking a take-it-or-leave-it offer), and there are special rules for the enforceability of contracts of adhesion. The principle is that they can't be too surprising or too unfair. There's a fair amount of case law about where that line is (which I mostly don't know).
Legally what's important is that you had the opportunity to read the contract before you agreed to it. In HN terms, as an example, you can't legally steal GPL'd code if you don't bother to cat LICENSE.md
During a first year university computer science course, students were told to line up and sign an agreement for access to department computer labs. Most of the students lined up, grabbed the paperwork when they reached the front of the queue, then promptly signed it. I decided to actually read the paperwork, which earned me the privilege of standing at the side until the task was complete. No sneaky clauses, for the better or the worse, in my humble opinion. I simply had the privilege of standing out.
Not that it really mattered. I walked away learning a different lesson since I already had access to their computer systems. I already asked for permission to access their systems, and was granted permission without doing the paperwork. For the most part, these agreements are intended to handle the typical case, and are meant to inform rather than be a rigid contract. (The irony: I consider trust as sacrosanct, so I often over comply with the rules.)