One of the most powerful things about historiography is that it allows us to approach the past through an infinite number of perspectives. History is a vibrant field, not only because artifacts thought lost to the ages occasionally turn up but because each generation of new historians includes those who look at the historical record and see a pattern that had been previously unseen. Or they ask a question in a new way, opening up a whole new perspective. That dynamic nature of "doing history" is what makes the most meaningful and interesting part of your question your first three words: "I have heard..."

Before we get to your question, it's helpful to start with a parallel one. Let's say I posed the question, "I have heard that Thomas Jefferson cheated on his wife, participated in orgies, witnessed and laughed at rape and did nothing to help her, and even raped someone himself. This was supposedly all public knowledge while he was alive but if that's true, shouldn't there be proof? Is any of this actually true or are people just trying to slander him?" If I asked my question in 1820 or 1900, it's very likely that's the answer I would get from a historian would highlight Jefferson's accomplishments and work to minimize the things I heard. Biographies of him from the era would stress his accomplishments and talk about the truly brutal nature of campaigning in that era and how candidates fabricated lies out of whole cloth and those things I heard about Jefferson? Likely just propaganda and campaign lies.

In 1915, Carter G. Woodson, the child of formerly enslaved parents and the second Black American man to receive a PhD, founded the Association for the Study of African American Life and History and The Journal of Negro History. In 1922, he published The Negro in Our History. In the book, he used the practices of historiography of the era to show the reader how African Americans, freed and enslaved, shaped the look of our country and were shaped by their history on this soil. He would go on to mentor and support the next generation of Black and African American historians who developed ways to engage with slave schedules, deeds, and artifacts from the era.

In 1975, Gerda Lerner wrote the foundational text for the field known as women's history. She wrote:

I learned in studying the history of black women and the black family that relatively high status for women within the family does not signify "matriarchy" or "power for women," since black women are not only members of families, but persons functioning in a larger society. The status of persons is determined not in one area of their functioning, such as within the family, but in several. The decisive historical fact about women is that the areas of their functioning, not only their status within those areas, have been determined by men. The effect on the consciousness of women has been pervasive. It is one of the decisive aspects of their history, and any analysis which does not take this complexity into consideration must be inadequate.

The contributions of Woodson and Lerner, among many others, to the field of history and historiography mean that were I to ask the exact same question in 1999, following the publication of Annette Gordon-Reed's Thomas Jefferson and Sally Hemings: An American Controversy and Fawn McKay Brodie's Thomas Jefferson: An Intimate History, the answer would be very different. Instead, it's likely a historian would help me better understand early America propaganda as well as the lived experiences of enslaved women at Monticello. Instead of treating Jefferson a "great man" and minimizing the choices he made, they would help me sit with the discomfort that one of the founders of my country had children with a woman he owned.

In the last few years, historians have taken another look at the historical records from the antebellum era and uncovered that white women had a much more active role in the slave trade than historians previously thought. They took a closer look at the archives from the Freedmen's Bureau and journals from the era and formed a fuller, more complete picture of the role of Black and African American educators immediately after the war. Finally, they've expanded the conversation about and debated the question of agency when talking and writing about enslaved men and women and how we talk and write about their consensual relationships and sexual assault. All of this means the answer to my question would be different today than it was a decade ago, then a century ago, then two centuries ago.

Which leads us back to your question. The short answer is that Martin Luther King, Jr. was a man. No more. No less. He was a man who was deeply unpopular with white Americans while he was alive and lived under the intense scrutiny of the American government. It's worth highlighting that the FBI didn't accept Black men into the academy until 1962, (according to their own website), almost 60 years after the Bureau was created and there is overwhelming evidence that the FBI - the organization or an agent - sent King a letter urging him to take his own life. Meanwhile, we only know what that letter says because it was discovered five years ago, while a historian was working on a biography of J. Edgar Hoover. Which is to say, what you "have heard" about Martin Luther King, Jr. has been primarily shaped by media coverage and federal agencies that were resistant to integration, if not openly hostile to Black Americans.

One of the most remarkable books I've read of late is A More Beautiful and Terrible History: The Uses and Misues of Civil Rights History by Jeanne Theoharis. She walks through how, in the modern era, mostly white Americans have taken people from American history and mythologized or demonized them, in service to our own goals. Part of what makes her book so powerful is her clarity around the harm it causes. She helps us sit with the harder and more important questions when it comes to King and his contemporaries. Questions like: What brought details about Kings life to your attention? What do we hope to accomplish as individuals when we focus on particularly unflattering details about his life? Why are we prone to mythologize or demonize activists for social justice? What are the implications when we remove King's humanity?

All of that said, this section of a recent piece Theoharis wrote offers lots for us to consider regarding connections between civil rights activists yesterday and today:

So let’s be clear: Martin Luther King Jr. and Rosa Parks and their many comrades were persevering, courageous and disruptive, and they made America uncomfortable—just like many people engaging in BLM movements across the country today. But we have stripped them of this history. By turning civil rights heroes like King and Parks into Thanksgiving Day parade balloons—happy, larger than life and stripped of their substance—we make them “unavailable for where we are now,” as the late Vincent Harding put it, “so we can keep ourselves comfortably distant from the realities [they were] trying to grapple with.”