Football has been called many things during its ongoing Premier League boom years. Overblown, overpaid, inexcusably self-important: this has been a common theme. At the same time there has generally been a sense of modernising forces at work, of a flushing out into the light from the dark days of the 70s and 80s when football was pretty much left to rot and fester like an obsolete piece of industrial plant. So much so that the events of the last two Premier League weekends have come as a horrible surprise. Almost 20 years on from the foundation of the Football Association funded anti-intolerance campaign Kick It Out, it seems it may be once again necessary to call football racist.

Albeit, there is an unexpected shift of angle here. It isn't the crowds who stand accused: instead it is the people on the pitch. Most shocking of all are the accusations made by Chelsea FC that referee Mark Clattenburg racially abused two of the club's players during Sunday's match against Manchester United at Stamford Bridge (using racist epithets, if the early reports are true, of the vilest kind). Bizarre and appalling as this sounds – and the FA is currently investigating – is it not an isolated incident. The previous weekend, several black Premier League players refused to wear T-shirts endorsing Kick It Out (but did this weekend) in protest at the perceived leniency of the FA's punishment of former England captain John Terry for using racist language towards another player.

In truth, this has been brewing since October 2011, when Terry was first accused – via YouTube and by a still-anonymous spectator – after a match against Queens Park Rangers. Since then, English football has endured a progressively damaging 12 months: Liverpool's Luis Suárez was banned in December for calling Patrice Evra "negro" (not once but seven times in two minutes). Terry was stripped of the England captaincy, acquitted of criminal charges, and then banned for four matches by the FA for use of the phrase "fucking black cunt" (he claimed he was caught in mid-denial, as in "I didn't call you …"). And now this.

Are we seeing the first rash of a much broader contamination? Or simply a flushing out of the worst, overwhelming much of the good? Until recently, English football has been hearteningly in credit on this front, not just in the obvious improvement in the stands, but in the perception that incidents were at least dealt with. That, unlike in many other European countries, the English FA would take a tough stance. That credit has been eroded. This week, the former England player Les Ferdinand suggested the FA has "let down all black people who are interested in football" with its treatment of Terry. The ongoing scarcity of black managers and black administrators 35 years on from the first generation of English black professionals also stands out starkly. All that really seems certain is that this is a pivotal moment in English football's attempts to police and eradicate racism – and that the battle is taking place in full public view.