How else do you harm the goal of silencing through intimidation other than not to cooperate with it, and as far as is possible make the tactic counterproductive?

As I've said elsewhere this presumes that this was, in fact, the sole or chief goal of the murderers. I'm not convinced it is. It was, to quote mollpeartree "an act of political theater" and art is notorious for allowing multiple interpretations (much like the cartoons from Charlie Hebdo).