just repeating that a service is not "ethical" because it is decentralized. the infrastructure and deployment model do not magically confer harmonious human action upon a service.
YouTube is decentralized for crying out loud. there's not one, enormous ~~YouTube Server~~ that runs all the youtubes. There are lots of decentralized servers, administered by countless people. the problems arise because of *how* the people who administer the service *behave*. that's where the ethics comes in--not in how the software is deployed.