It is not possible to determine why Martin Luther King Jr. would express his apology in a specific way without more context. Martin Luther King Jr. was a civil rights activist who fought for racial equality and the end of segregation through non-violent means. He made numerous speeches and statements throughout his career, and the specific way in which he chose to express an apology would likely have been influenced by the context and purpose of the apology, as well as his personal style and beliefs.
It's important to note that Martin Luther King Jr. was a great orator and his speeches were carefully crafted to deliver his message and inspire people to action. He often used powerful and emotive language to convey the urgency of the Civil Rights Movement and his speeches were often seen as powerful calls to action. He also often used biblical allusions, metaphors, and rhetorical devices to make his speeches more powerful.