Anarchist pacifism implies that all violence is wrong because it is inherently authoritarian as a force being imposed upon another being.
This analysis however doesn't take into account the systematic nature of violence inherent in certain social relationships (like that between the police and the policed) and considers violence directed against the power holders in these relationships to be the same as attacking a random person on the street.
While others may view "inverted class-violence" as self-defense in an already violent situation, the anarchist pacifist may maintain for example, that the pre-existent violence of private property is not worse than the violent expropriation of such property.