Your post made me think that that bank did not care much about that person and personnel in general. Few fails at work, caught gambling - got fired. In someway I think it might be more human to try to help that employee with his gambling. I dont think that bank fired him immediately when they saw him gambling for first time. I think there were talks, warnings before firing that person. If they see a person has problem, it would be best to help him. Instead, now he still had this gambling problem, and now he is jobless in addition. Bank made his situation from bad to worse.
If the guy didn't used customers' money then there was no need to fire him because that is what pleases him to do. That is his own choice. If he was doing his job well then there was no need fire him that was doing his work diligently. From my own understanding of the whole thing, the sacking of the Banker is beyond the gambling habit. Probably he has been borrowing from the.bank and using it to gamble and he has been reported and warned but gave deaf hear but when it was obvious and he was fired.