There is no such thing as "natural" search results, the search results are the result of complex interacting algorithmic logic that Google implements to try to give you "good" results.

When Google for instance penalizes a site for being slow; or for being spammy; or being identified by the algorithm as likely to be disliked by most users, and not be what they are looking for; or for having spyware; or for seeming to use "black hat" SEO with irrelevant keywords...

...are these actions "censorship"? What kinds of shaping of google results are censorship and what kinds aren't?

The results are inherently shaped, they only exist because of algorithms that implement choices, there are no "natural" unshaped results.