What do propaganda and censorship have in common?

When Propaganda is being used their is an explicit attempt to highlight one aspect of a situation favoured by the person doing the propagandizing. In order for propaganda to be effective the same message needs to get delivered from multiple sources (various media, different government institutions, by public figures, etc...) the message must be straight forward and delivered consistently over a period of time.

Competing ideas or positions serve to diminish the impact propaganda and provide more information and perspectives to the public which may not support the propaganda effort. The goal is to put out one opinion and have everyone take on that opinion, having many opinions/perspectives dilutes the propaganda effort.

Censorship can be explicit by forcing media and people to not challenge the messages being sent (for example under the threat of arrest) It can be implicit/tacit by privately speaking to key decision makers and getting them on the side of the propaganda, or ridiculing all other options, or for example getting advertisers to stop buying advertising is magazines that don;t support the propaganda position.