Coventry narrowly avoided relegation at the expense of Sunderland during the 96-97 season. Obviously rather than this just being a simple twist of fate the residents of Mackemland have taken this personally and now hold a grudge against them. Basically, imagine us despising Hull for daring to finish one place above us when we went down because that's more or less their problem.
I posted the bit below, are you sure it was 96-97?
It goes back to May 1977, I think. The Mackems were relegated basically becaue Coventry and Bristol could have also got relegated so Coventry managed to get the game delayed for 15 minutes or so. Coventry and Bristol only needed a draw once the mackem result was known and they both p*ssed about for the last 15 minutes knowing that they didn't have to win the game.
Coventry should have been shafted for that because it was almost certainly a fix, it was funny though at the time.
Edit.
http://en.wikipedia.org/wiki/Jimmy_Hill
Despite his surprise departure as manager in 1967, Hill returned to Coventry City as managing director in April 1975 before becoming the chairman. As chairman, at a crucial relegation match at home to Bristol City at the end of the 1976–77 season, Hill delayed the kick off by 10 minutes for fans still outside caught in the heavy traffic. Relegation rivals Sunderland, playing at Everton kicked off on time. Sunderland eventually lost the game 2–0. Knowing that all Coventry needed to stay up was a draw, the Sunderland result was flashed up on the scoreboard. Hill made his players pass the ball around in their own half for the last 10 minutes of the game, saving Coventry from relegation at the expense of Sunderland, Tottenham Hotspur and Stoke City. Hill was never forgiven by Sunderland fans.
Jimmy Hill , the original Troll:
http://i.imgur.com/tfRfx.jpg