Censorship, which is to say the total obligation of restricting publishable information, by state, corporation, or any other similar group or entity, fundamentally destroys human thought. It goes against principles of free speech and free thought, by which minds can contemplate all things.
Censorship can also be argued to include an individual acting alone to restrict such information. The "ethics" of that depends entirely on if one even believes ethics exist, but I shall act under the assumption they do to satisfy your particular question.
A man stopping another from stabbing him protects himself from harm. A man stopping another from inciting a crowd of people to want to kill him similarly is protecting himself. Even reducing these instances of life endangerment to mere bodily or reputational harm, they still carry with them an evident defense.
So long as "censorship" is only making obvious the truth and preventing lies and misinformation being spread, WITHOUT restricting a topic as a whole, debate over the truth, or hypothetical discussion regarding the matter, it is ethical.