I read the article, and it struck me as dangerous. I'm going to be somewhat vague and say that the article caused two potential forms of danger, one unlikely but extremely bad if it occurs and the other less damaging but having evidence(in the article itself) that the damage type had occurred. FWIW, Roko seemed to agree after some discussion that spreading the idea did pose a real danger.

If some of them had decided the censorship was unjustified, LW might look like Digg after the AACS key controversy.

In fact, there are hundreds of deleted articles on LW. The community is small enough for it to be manually policed - it seems.