Censorship is suppression or prohibition of content. Putting wikipedia on IPFS makes it strongly resistant to many forms of censorship because it uses content-addressing. This means that suppressed content can be redistributed through alternate channels using the same cryptographically verifiable identifier. It also means that you have clarity about which version of the content you're viewing, so if some entity publishes a censored version of your content you have a way to distinguish between the two versions.

If you suppress it in one place, people can put it up somewhere else. If you block one path, people can make the content available through another path. If you modify it, people know that you modified it, have clear ways to distinguish between your copy and the unmodified copy, and can request the unmodified version without wondering which version they're getting. If you destroy all the copies on the network, people can add new copies later and all of the existing links will still work. Etc...

IPFS can't protect people from a government physically tracking down every copy of the censored content and destroying it -- that requires other efforts external to the protocol (ie. move copies outside their jurisdiction). It does, however, make it possible to move many copies of the content around the world, passing through many hands, serving it through a broad and growing range of paths, without the content losing integrity.