Rivalry between Manchester United and Liverpool fans

The disharmony and rivalry between Manchester United and Liverpool players arise from the 1990s & early 2000s and they practically ignored to each other.
Sir Alex Ferguson,the Scottish manager exactly wanted the same to have the rivalry among the  teams and had no interest in bring the harmony to these teams. His players would be called up to play for their country, then risk injury and upsetting his plans.
Liverpool's players viewed the Manchester United as straight-laced, too focused and one dimensional on football where Manchester United's players considered Liverpool's flash and think above their station without any medals to back up their self-assured arrogance.

Rivalry between Manchester United and Liverpool fans

Alex Ferguson's greatest achievement once said was knocking Liverpool off to the perch as the kings of English Premier League football. The outsiders, entering either in the changing room took some time to get used to nuances of the greatest rivalry in the  English Premier League football, but most got it.
Not Jordi Cruyff and Gabriel Heinze, though -- they could see no issue in joining Liverpool until such ideas were knocked out of them by the teammates.
Ferguson's trusted assistant manager Carlos Queiroz recalls the feeling among United's players."I sat in the dressing room at Anfield. We'd played a Champions League game midweek and the boys were very tired," he said. "I didn't think we had a chance. The boys were quiet, but then something magical happened in the tunnel at Anfield, near that "This Is Anfield" sign.
"The boys were transformed as they walked onto the pitch. I couldn't believe it. They walked out and looked at the away fans to their left and then to the Kop singing 'You'll Never Walk Alone'. The United players knew they couldn't be beaten. They had so much enthusiasm and pride in playing for United they won the game.
"They knew they couldn't lose, that it was in the DNA of a United player to be at his best against Liverpool."