First of all, people are taking this situation way too seriously.
Ignoring everything else, when is it against the rules to not use all of the advantages available to your team? If I decided to not use the three upgraded cards every round available to me for the rest of the war, would that be breaking any rules? I'm just confused on some of the points made here.
I think this is a good point to raise because a lot of people are unclear about it.
As in your example, choosing not to use the three upgraded cards every round would be completely legal; that's your choice and you are accepting both options, then picking one. Nothing wrong with that.
When does "not choosing something" become illegal? Here's the answer:
Let's start with a hypothetical. Let's pretend that the event card had said that all Light cards for the round
had to be upgraded. (Obviously it would never say that for several reasons but let's just say it did).
In this case, the community would have been equally outraged and the same actions taken. However, those actions would now actually be against the rules (because not using upped cards goes against what the event card says).
How is this hypothetical situation different from what really happened? Substantively, it is identical, except for the technicality of the rule. So when players interpret this situation as a giving up of an option to use upped cards, that's not really an accurate view; they wouldn't have been building their decks individually and taking the option of using unupped cards for specific reasons (e.g. I don't have the upped card / I prefer the unupped version's casting cost). Actually what they would have been doing was to
remove the option of using upped cards altogether. The end result is the same thing as choosing not to, but the modus operandi was actually to ignore the event card. In general, ignoring event cards is of course against the rules.
In other words, it's basically a coincidence that this particular event card gave an optional bonus rather than a required one. So, ignoring the event card (which is against the rules) happened to coincide with a legal version of play which would be to use the event card but choose an option with the same result (no upped cards).
That fact doesn't change the illegality of ignoring the event card.