That's possible if they're using only network-global review and reputation system. If they're also relying on WoT-like reputation system where peers rate peers

That's possible if they're using only network-global review and reputation system. If they're also relying on WoT-like reputation system where peers rate peers, and reputation's calculated from those chains of trust, massive sockpuppet attackers won't be able to quickly erode trust, as they'd generate that trust only throughout their own circle, having minor impact on others. They'll have to play by the rules for a long time to spread connections through the network.