the people who read LW are hopefully rational enough not to run out and commit violence based on a blog post

Anyone can read LW. There is no IQ test, rationality test, or a mandatory de-biasing session before reading the articles and discussions.

I am not concerned about someone reading LW and commiting a violence. I am concerned about someone commiting violence and coincidentally having read LW a day before (for example just one article randomly found by google), and police collecting a list of recently visited websites, and a journalist looking at that list and then looking at some articles on LW.

Shortly, we don't live on a planet full of rationalists. It is a fact of life that anything we do can be judged by any irrational person who notices. Sure, we can't make everyone happy. But we should avoid some things that can predictably lead to unnecessary trouble.