It's ironic that Diouf is remembered and castigated for spitting on an opposing team's fan. Now, I am not condoning Diouf's behaviour which was vile and disgusting after his pace took him into the crowd and a fan 'patted' him on the head. Diouf's solicitor, Joe Beltrami stated in his client's defence that in Senegalese culture it was "degrading, insulting and patronising" to be touched in such a way on the back of the head because in past years slave traders had done that.
However, Eric Cantona karate-kicks a verbally abusive fan at Crystal Palace and goes on to become one of Manchester United Greatest Ever players. Of course Cantona jusififyably received a lengthy ban but Man Utd and manager Alex Ferguson stood by him. Cantona got which most offenders deserve, the perverbial second chance probably because of his great skill and importance to Man Utd.
On a side but connected issue we have another spitting incident where Celtic's new signing, Chris Sutton grogs on a man with his family coming out of restaurant after words are exchanged.
Sutton is rightly fined in a court of law but goes on to have a career playing for Celtic then later in football punditry.
Three 'similar' incidents involving involving certain teams, players and opposing fans. I reckon Diouf perhaps inexplicably suffered the most. Cantona and Sutton less so due to a compliant media not willing to cross Alex Ferguson or those I/c of Celtic at the time.
I like to think that Walter Smith signed Diouf for many of the reasons stated in this thread but also because he was a player who deserved his second chance at a big club like Rangers similar to what Cantona and Sutton got at their respective clubs.