Answer: It is related to the shootings at a screening of The Dark Knight Rises. The perpetrator dyed his hair red and was reported to have referred to himself as ‘the Joker’ at the time.

There are those who believe that the version of the Joker character depicted in the film - a man with mental health issues who is badly mistreated by strangers who snaps - will inspire people in real life to do the same. Particularly, outlets like io9, who you link to, who identify so-called ‘incels’ as one such group of people.

The film has received critical praise at the festivals at which it has been screened.