Because they are mutants too? And if they accept Apocalypse and his likes, why not the precogs?
If a oracle tells you to do something horrible for the greater good, will you do it? In a way, precognition is a god-like power that places a terrible burden on anyone's shoulders.
Heroes are models that shows that things that we consider impossible are possible, it is liberating.
Following oracles is being precogs' puppets.