Not exactly; the idea is that some people (I don’t agree with this) hold that it is not possible to be racist or sexist against the empowered class. In general, that would mean that it’s not possible for a white to be racist (and, let’s face it, it’s hard. There simply isn’t a nasty word for white people that has any sting at all.)
If you were to look at a setting like a majority-black neighborhood, where a white neighbor gets treated badly, excluded, disempowered, refused service, then that would be racism. So the concept is context-sensitive. Another example is the public library system in many cities, where librarians are nearly always women: men trying to break in to the profession have to fight an uphill struggle against this entrenched sexism. So women can be sexist, but only (per this definitional concept) when they are the ones in power.
So, it isn’t just self-serving definition, but a definition based on social power.