If they were in school they would be made to sit apart until the end of term. Barcelona and Real Madrid bring out the worst in each other.
Barca, anticipating the opposition's over-physical approach, exaggerate the theatrics. Madrid -- and more specifically Jose Mourinho -- believe the opposition cannot be beaten at football and so do everything in their powers to stifle the beautiful game.
Mourinho quoted Albert Einstein before the game, citing willpower as the only force greater than atomic power. Another Einstein gem came to mind as for the fifth game running his side finished a match against Barcelona with 10 men: "Insanity is doing the same thing over and over again and expecting different results."
Barcelona were not blameless. Just as Sergio Busquets exaggerated Thiago Motta's foul in last season's semi-final against Internazionale so Dani Alves helped make sure Pepe walked for a challenge that, while a little wild, barely made contact with the full-back.
The spectacle as a whole suffered. The watching world had tuned in to see the greatest players on the planet but -- Leo Messi's sublime goal aside -- the enduring images are of the referee being shielded by riot police as he left the pitch, Victor Valdes having a laser shone in his face, a half-time brawl on the touchline and Pep Guardiola urging his players to get off the pitch at full-time as missiles rained down.
Mourinho's record against Barcelona is dreadful. In 15 games his sides have suffered seven sendings-off. His teams have failed to finish their last five games against them with 11 men.
"If you play with fire you get burned," said Gerard Pique. "It's no coincidence that this always seems to happen to him." Mourinho has admitted that the battle begins in the press room before the game and this assertion seems to underpin another belief that Barca can't be beaten with just 90 minutes of football.
He creates the hostile environment in which reckless challenges and sometimes reckless refereeing decisions are more likely. His tactics also tend to strangle the possibility of an open football match where the referee might pass relatively unnoticed.
Even Cristiano Ronaldo seemed frustrated by the tactic of letting the opposition have the ball until they approached Madrid's final third. Barca's possession was 82pc in the first 15 minutes and before he was substituted at half-time, Real's gifted Mesut Ozil had made just two passes.
He soon was back on-message, echoing his manager's conspiracy theory: "These boys (Barcelona players) have a lot of power off the pitch."
Uefa will deal with that particular accusation over the coming days. (© Independent News Service)