You're wrong.
favouritism
noun
1. an inclination to favor some person or group [syn: favoritism]
It doesn't matter if the reason for that inclination is reasonable or unreasonable. If you are favouring the son that acts responsibly with your wealth, that is still favouritism. If you are favouring the ethnic group that commits less crimes by putting less of them in Analrapea, that is still favouritism. To not play favourites, you have to treat all groups equally...
...Despite them not being or behaving equally.