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

The ANTONYM of the word INNOCUOUS is:

Harmful

The correct answer is Option (2) → Harmful

• Innocuous (Adjective): Not harmful or offensive.

• Harmful (Adjective): Causing or likely to cause damage or injury. This is the direct opposite.

Other Options: 

• Inoffensive is a synonym for innocuous.

• Gentle is a synonym for innocuous in the sense of being mild.

• Insightful means having or showing an accurate and deep understanding; unrelated to harmlessness.