The mere fact that Richie has committed a criminal offence should not automatically lead to his dismisal.
However, despite the relativley modest fine which reflects his early plea and the fact that he appeared as a first offender, possession of a class A drug is not a trivial offence.
In my opinion, if Richie at any stage misled the club about his involvment that amounts to gross misconduct and he should go. If on the other hand he has been honest with the club from the outset I believe that he should be issued with a final written warning making it very clear that the club deplores his actions and that any further misdemenour WILL result in his contract being terminated.
The situation with the St Johnstone playes is entirely different as that was only ever a matter of allegation never prosecuted and never admitted by the players at any time whereas there is now no doubt that Richie has committed a not insignifigant breach of the criminal law.