What I believe to be systematic bias against Arsenal has been going on as long as I can remember.
People were unhappy we brought in a foreign manager in Wenger. We started competing with Ferguson with an entirely different brand of football that wasn't very english at all, and with players of different origin. A lot of the bias against Arsenal probably stems from us simply not being British enough (with jealousy of our way of playing also being a huge factor). I also think Ferguson played a large part in creating an anti-Arsenal bias. Ferguson's response to us having a better team in 2002 was to just kick lumps out of us, and referee's, afraid of Ferguson - which was recently acknowledged by Mark Clattenberg - let them get away with it. The likes of Allardyce decide I'll have a bit of that and the era of "Arsenal don't like it up them" was born. It was never called out, and in fact it was celebrated. That culture led to the career changing injuries inflicted the likes Diaby, Eduardo and Ramsey.
Teams could kick us as much as they wanted to and get away with it. I genuinely do believe there has been corruption and match fixing going on as well. Won't explain that with another long ramble yet again though. Mike Riley is now the head of the PGMOL though. He is the man who infamously ended Arsenal's 49 game unbeaten streak with the single most ridiculous refereeing display I have ever seen.