Not at all, and I don't know where you are getting that idea from. The system, as it is designed right now has no requirement for a single centralized or trusted party. It also has no requirement for any trust between the participants (which most systems in the same realm do).
> What will you do in polemic cases?
That's a good question, and one of the things we want to explore during iterations of the testnet. Without going into more specifics I would say that there is a part of the incentive mechanism that rewards a more clear-cut consensus (a 50/50 split on a boolean statement is the least favourable situation for participants on both sides). This unfavourable situation should then in turn fuel the contribution of more information so people can make a more informed rational decision which should then lead to a more clear consensus. There are also some higher level market mechanisms that we anticipate to develop which could be used to both stabilize and destabilize the consensus about a certain statement, like a off-chain PR campaign as you mentioned. We'll have to see how each of those can potentially impact a consensus and if that is something that needs a countermeasure in the core protocol.
What will you do in polemic cases? For example, some people think that La Gioconda is own by the Italian people and should be returned to Italy (because Leonardo was Italian). What would you do if there is a huge campaign to claim that it is owned by some Italian museum? What about the Tutankhamen mummy? Alaska?