It was when Deadmau5 had has rant about there being no real DJs anymore, just producers claiming to be DJs for an extra pay check or something. Jackmaster responded with a list of DJs including himself, Erol Alkan and Oneman among others. Deadmau5 tried to end it with a passive aggressive complaint about needing to get some work done and Jack immediately responded "no thanks we've all suffered enough of your work already. Go pick a fight with Madonna at least she's worse than you."
Tiesto responded with the same as Afrojack as well. I don't entirely hate Deadmau5, he's done a couple of tracks that weren't total shit and I suppose he did go back to back with Richie Hawtin but he's such an utter fuckhead on social media that it negates any good he does.