What is the term for words that can escalate or de-escalate a situation?

The term you're looking for to describe words that can escalate or de-escalate a situation is not the either-or fallacy. The either-or fallacy refers to a logical fallacy where only two options are presented as the only possibilities, ignoring other potential alternatives.

In the context of communication, effective speaking involves using language in a way that influences how others feel and react. This encompasses the ability to use words that can calm a tense situation or, conversely, intensify emotions.

Mutual understanding focuses on achieving a common perspective or agreement among individuals, which can indeed contribute to de-escalating a situation but does not specifically address the power of words themselves.

Body language plays a crucial role in communication but pertains to non-verbal cues rather than the verbal choices made that can influence the atmosphere of a conversation.

Therefore, the concept that relates specifically to how spoken words can intentionally change the emotional tone of a situation aligns with effective speaking.