First of all, you shouldn't really keep African and South American together because quite often the pH requirements are quite different. Where South American fish live in mostly low pH, Africans live in very high pH.
Now that is a strange question, if you don't want it, why don't you just take it to your local fish store, I'm sure someone else will be glad to have it.
The people you have been talking to obviously don't really know the Oscars, Oscars are not the vicious killers that people like to make out. Yes Oscars will eat small fish if they get the chance. However you might just find that your Oscar lives in harmony with the other cichlid