The speech given by him seemed to be INNOCUOUS but there were undercurrents that implied the contrary:

The ANTONYM of the word INNOCUOUS is:

Option 1 -> Inoffensive means not causing offense or harm, which is actually a synonym of innocuous, not an antonym.

Option 2 -> Harmful means causing damage or injury, which is the direct opposite of innocuous (harmless).

Option 3 -> Gentle means mild or kind, which is similar in meaning to innocuous rather than opposite.

Option 4 -> Insightful means showing deep understanding, which is unrelated to the meaning of innocuous.

Hence, Option 2: Harmful -> Innocuous means harmless or inoffensive, so its antonym would be something that causes harm or damage. This aligns with the context where the speech appeared harmless but had dangerous undercurrents. -> correct