Firstly: Research questions focus your topic from something very large into a more focused query that you can answer in your assignment. Sometimes assignments focus on a single large research question, others build in multiple smaller questions.
"Martin Luther King Jr.?" is not a research question. "Did Martin Luther King Jr.'s rhetoric conflict with Malcolm X?" is a research question.
Secondly: Research questions allow you to use multiple concepts to create a more powerful search. Databases don't always produce good results when searching for a single concept.
I would type "Martin Luther King" and "Malcolm X" and "rhetoric into LionSearch, or a related database to research this question.
Focusing the Scope of a Topic
It is very easy to go overboard with really big ideas! Remember, a quality topic is one that you can address thoroughly in the full length of your assignment. Avoid single concepts, generally. Some examples are:
Entire wars or conflicts.
Social problems that are constantly discussed (ex. Partition, segregation)
Instead think about focusing on:
How a specific group was affected by a war (ex. how children were affected by the Bangladesh Liberation War)
A specific element of a social problem (ex. how segregation affected the education of doctors)
It's also very easy to get an idea that is so focused that it is essentially impossible to research, often because scholars just haven't looked at that issue yet. Check when you pick a topic that you can find a variety reliable sources on what you plan to address. Some examples are:
Why a little-known athlete was affected by segregation.
How a single video game was based on Ghandi's rhetoric.
Instead, think about focusing on:
The racial system that allowed excellent athletes to be ignored despite excellent performance.
Ghandi's lasting influence on media sources of all types.