What are the ESSs among hawks, doves, retaliators, bully and prober retaliators?
I think Dawkins answers this in the book as well.

The point was that most strategies are not stable because the "random" introduction/mutation/evolution of some alternate strategies will disrupt a population of the first strategy. 

The example was a group of doves being invaded by a single hawk (the conspiracy of doves). Because the hawk does relatively better (by winning every conflict against a dove), than even after generations of entirely doves, the random addition of a hawk (say by mutation) will take hold because the hawk always wins against a dove. Whatever feature/gene that created a hawk in the pool of doves will be passed to some offspring.

If I remember correctly, the only stable case was prober-retaliator, since all others get invaded by someone else.