If moderation is just the current group in power gets to decide what is moderation and what is censorship then I fail to see the difference. You just redefined the centralization because I guarantee that group will be smaller than the rest of the internet.
Yes, but this isn't some kind of repudiation of the concept. One person's justice is another person's injustice. One person's virtue is another person's iniquity. Moderation is a necessary component of any civil social structure.
if Facebook actually had a PR position of "we remove whatever the hell we want" it would be fine, rather they prefer to have nice sounding rules and then interpret them however the hell the want.
Personally I have a similar position towards net neutrality... if my isp wants to degrade connections to torrents and netflix/youtube that is fine, but the have to put it in writing in the contract.
punishing someone for breaking the rules - not vague "we reserve the right to fuck you in the ass for any reason or no reason at all" kind of bullshit rules employed by facebook/twitter/reddit/whatever - is not considered censorship even at the kinds of places where people are particularly sensitive to it - for example, people don't accuse moderators of censorship when someone posts porn on 4chan's safe-for-work boards and it then gets deleted.
besides, facebook/twitter/reddit/whatever, despite being centralized and authoritarian services, aren't equipped to combat abuse any better than decentralized entities, the only difference being that instead of blatant low-effort buy-penis-pills spam they are targeted for subtle manipulation at industrial scale.