It seems like there are two questions here - words that do not incite negative emotions like anger or fear, and words that are not justifiable cause for those emotions. "Benign", alwayslearning's answer, satisfies the second but not the first - since, I think, there fundamentally are two concepts suggested here.
As for the other, if you're avoiding positive goods like "soothing" or "comforting," I like "innocuous" (even if it technically begins with a negative prefix). Strictly it means "harmless" (https://en.wiktionary.org/wiki/innocuous), but it can carry connotations of not even seeming dangerous.