Real-world pricing errors are a thing, you understand this, correct?
Yes, in fact I've taken advantage of them on more than a couple occasions. However, when it was clearly a pricing error, as in this case where a digital license with a typical cost of $50 was priced at $0, and there is no exchange of currency, then there is really no reason to be upset when this thing you got for free isn't honored.
For example, if I were to walk into a brick and mortar store and see a brand new game with a $0.00 price sticker on it, take it to a register and be denied the sale, there's no reason I should be upset. Why? Because logic tells us that this is an error which I knew of and was trying to take advantage of. In the same regard, if one were to see an item on a shelf, put it directly in one's pocket and walk out, one can't be upset when they are stopped by security because they knew it was wrong.
Now, we take these same real-world concepts and apply them to this digital "purchase"(with no actual money exchange, this is a stretch of the word). They knew in their heads that this price was an error when those who took advantage of this put the item in their cart. Why then should they reserve the right to be upset when this thing they knew they were taking advantage of was clearly an error?
If we were talking $5 or $10 error, then your "pro-corporation bs" comment would have a little more validity, but as it is you're calling what is actual business something that is it not. Say you're selling something on a shelf with a price tag under it, someone rips off that price tag and says "No, it didn't have a price on it. It's free.", would you give that item to them? Let's say you do, and the next person in line does the same thing. Do you give it to them as well? At what point do you return to trying to actually sell your product versus giving it at the price it is "advertised"?
This digital transaction was tantamount to stealing a full price item, and I can't think of any reason why someone would be upset, except for the "I got caught and can't have this now" crowd.