When talking about logos, we look for strong words and phrases, as well as repitition.
1. Elimination
The answer is surely not "It relies on the use of the word 'amazing.'" This is because it is not important, and not repeated. If we were to remove this word, this secton of the speech would still be powerful.
The answer is not likely to be "It focuses on the use of negative words." This is because negative words are not included in this, so there isn't a focus on them.
The answer is not "It points out differences in religion" because mentioning religion was a small detail. It doesn't point out the differences in religion, but rather points out there are different religion. Nonetheless, this is just an example to prove MLK's point and wouldn't be right anyway,
2. Conclusion
Because we have eliminated all answers but one, we skip a few steps. We now must justify why the answer is the remaining choice.
The answer is most likely "It explains what 'all men' means and what it includes." This is because not only is this statement the evident main idea, it also includes the powerful repitition that is utilized to display a message.
If we were to apply this to another section of a Martin Luther King Jr. speech, "I Have a Dream", we would find the answer includes thw words "I Have a Dream". This line could be considered the most quotable and well-known quotes related to social justice. The line is repeated many times, with elaborations, just as "all men" is.
Please let me know if this helped, or if you have any questions! If you wouldn't mind, I'd be very grateful for a rating! Thank you!