Let me explain the situation.

Last year DOTA had a halloween event called "Diretide". Since TF2 halloween event happens every year, and the flavor text of Diretide said it was a annual event (like WoW Winter Veil", people started getting hyped.

There was no Diretide, and the shit hit the fan.

Disgruntled players starded spamming twitch chat with emotes, which eventually changed to people losing on purpose in-game to "call Valve's attention" and finally to defacing Wikipedia articles and raiding the game Metascore.

Again, because there was no holiday event, which by the way, lots of people complained last year because it was imbalanced and was delaying the release of new heroes.

But remember, the issue is not about the event (or lack of it) but about "Valve's disrepect and lack of communication for the community" about a event which  people expected to happen thought it was never officially announced or hinted in any way.

I can only think people at Riot can't stop laughing.