I think you're underestimating the volume of stupid-and-crazy shit that CS reps have to deal with every day. Sorting out stupid-and-crazy from legitimate-but-not-my-department would be several full time jobs in itself.
You've touched on a larger issue that occurs to me often. Though your point is valid, my response to a company making the argument would be, "too bad." /They're/ the ones making billions in revenue by voluntarily accepting a business relationship with millions of customers. If you want the revenue from those millions of relationships, it's also your responsibility to manage your side of the bargain with those millions of relationships, that includes your legal (and many other) responsibilities. Is scaling to keep up with your responsibilities to millions of customers easy? No. However that's not the customer's problem.
And yet, they're making billions despite not doing what you say. So...
It would not be in the interest of 99.9% of your customer if you try to to satisfy those 0.1% of stupid-and-crazy customers. Because somebody would have to pay for it. And in this case it wasn't even a customer.