Now I myself don't particularly care about Gangplank being disabled (I do not play him often, nor is he in my top 5 of favorite champs), but I can understand the frustration and anger of the people who are _**pissed**_ about Gangplank being disabled due to the lore event.
A fair majority of those people don't give a crap about Lore whatsoever, and waking up to see one of their favorite champs (and someone who they potentially bought with Riot Points) disabled due to something that happened in a story event most likely feels like a big "Fuck You" to them from Riot.
And so far all the Riot Employee responses I have seen on the matter (when they deign to actually respond) have been nothing but jokes - joking about how it sucks Gangplank is dead, how he is disabled strictly because of lore and not a bug, etc...
That does nothing more than raise the player's ire at having their concerns dismissed so easily by the people who are supposed to take their feedback.
So I was reading up on the matter and noticed that China had a really good solution for this - instead of disabling him entirely, they instead disabled his default skin, along with every other skin _except_ for Spooky Gangplank, which was given (or is temporarily given) for free to people who own Gangplank.
This I feel is a fair solution to the matter, as it allows people who love/like Gangplank to continue playing him (albeit forced to do so with a skin they may not like) whilst allowing Riot the "satisfaction" of tying Lore into the game itself.