I would ask you kindly to read this article from The Atlantic, a source I think most would agree is generally credible: https://www.theatlantic.com/magazine/archive/1995/09/slavery-and-the-jews/376462/
Ultimately, the positioning of the slave trade on part of Professor Tony Martin as being predominantly or even majorly funded by Jews is tenuous at best and the information he presents is not easily verifiable; the fact that he cites Jewish authors (which, you'll see in the article comes with enough problems to cast quite a bit of doubt--again, it is not uncommon for any person of any race/gender/religion/sexuality to either be wrong and/or hate themselves and their identities enough to falsify or inflate information that reaffirms the sense of "badness" they feel attached to those categorizations. See also: Clarence Thomas or Ben Carson, among many many more from truly every single background; this is part of the human condition) in order to corroborate his case doesn't make it any less of a myth or an over-inflation of Jewish involvement. If you research today George Soros or the Rothschilds you will also see conspiracy theories about Jews funding the most insidious evils that have been cast upon this earth.
The main issues that I'm still experiencing with what you're saying is that there is that there seems to be very selective (though no doubt unintentional) choices to A) believe precisely what Professor Tony Martin said as incontrovertible truth despite all of the other prominent and easily verifiable historical information that indicates otherwise (i.e. deliberately choosing to buy into what could easily be considered a conspiracy theory against Jews rather than accept the fact that yes they played a shameful and trivial role but it was clearly not a predominant or major one). The number of Jews alone, along with the notable marginalization they'd been experiencing, combined with the absolutely monstrous and literally world-changing, well-known violent imperialism that was committed by these wealthy countries/empires around this time (and clear historical records of their plans and executions of the slave trade--aside from the fact that they were all already doing it in their own countries long before the African slave trade begun) makes it so confounding and improbable that Jews would hold such a major role in the process that it almost seems like one would have to literally go out of their way to twist the history in order to place major blame on the Jews. Again, Jews are not perfect or excused in the context of this horrific historical event, but the decision to inflate their involvement in order to place additional unwarranted blame on them in what clearly seems to be a conspiracy theory reeks of antisemitism.
B) Selectively choosing to consider what happened to Professor Tony Martin explicitly as harassment, rather than something that he may have possibly brought upon himself is also disconcerting. The book he wrote was literally called "The Jewish Onslaught," a title so flagrantly antisemitic that it essentially undermines any possible integrity or veracity of his argument to begin with (the assertation that there is an "onslaught" of Jews attacking one for merely trying to express themselves or worse, trying to free real, factual information from suppression, paints ALL Jews as violent mobs who are attempting to control and stifle people and information, which is vile and antisemitic). If you do a simple search on Jews controlling the slave trade, you'll see a glut of results almost exclusively from either white supremacist websites (which also write articles about eugenics and other nonsense) or websites that contain the same rhetoric held by the Nation of Islam. Which, incidentally, Martin's book's title page proclaims that the work was "prepared by the Nation of Islam." The selection of material that Martin had assigned his students was selectively and specifically antisemitic falsities; as a matter of fact, the history of profound and unapologetic antisemitism runs so deep within the Nation of Islam, not only have they been condemned for it by esteemed organizations like the Southern Poverty Law Center, but they are notorious for peddling the precise kind of antisemitic propaganda uttered in the very book you reference. Their leader, Louis Farrakhan has in the past ten years publicly and unapologetically discussed how Jews are Satanic termites, and the rest of their ideology rests on other similarly violent, clearly false and cruel attempts to vilify all Jewish people.
https://en.wikipedia.org/wiki/Nation_of_Islam_and_antisemitism
My point is here, why would one be so quick to condemn what happened to Professor Martin as "harassment" as opposed to being rightfully condemned for perpetuating antisemitic tropes that ultimately cause real, even physical harm to Jewish people? The proliferation of these kinds of myths not only result in things like vandalism of Jewish businesses and places of worship, but attacks in the streets. A visibly Jewish man was murdered by antisemites in Baltimore last month as his assailants shouted antisemitic slurs at him. Countless others have been attacked; one orthodox woman walking in central park got a concussion from eggs thrown at her skull. There are many organizations keeping track of antisemitic violence, and there is a sky-high correlation between events that incur higher rates of antisemitic hatred and rhetoric and actual physical and verbal attacks on Jewish people and their livelihoods. That should not happen to any group of people. That is frightening and discriminatory and hateful and wrong.
This is why we have accountability even when there are behaviors that don't fall into the scope of what our legal system creates space for. Do I think that Louis Farrakhan should be in jail? No, he has a right to free speech. But I also don't think that he deserves a platform on mainstream news or even in universities in order to spew the kind of hateful rhetoric that will result in more attacks on my people. This is why Twitter and Facebook made their paltry attempt to remove QAnon from their platforms--people receiving disinformation about COVID and moreover people receiving inflammatory information that drove them to attack the United States Capital was deemed harmful enough that even the free and protected speech that they were consuming had to be faced with some accountability. Antisemitic hatred works the same way. Anything should work this way; if we want to have free speech in our society, we must find ways to effectively deal with the paradox of what some will perceive as "stifling" it when it crosses over a line into something unequivocally harmful and erroneous.
Based on the virulent success of QAnon, I think it's clear that there is a biological appetite in most human beings for "insider" information--information that most common sense and credible sources would deem incorrect but that feels accessible and illuminating (confirmation bias) to an inside group of people who are "wise" enough or privy enough to be able to handle it. This is why conspiracy theories are so popular and so dangerous. They both generate real and tangible and hateful consequences within society at large, and reflect the underlying hatred and biases that fester there to begin with in order to give wind to so much nonsense.
My question for you and for anyone else holding onto these ideas that they presume must fundamentally be true is, why, in spite of the vast majority of information out there that suggests otherwise, do you believe this must be true? With enough digging and enough honesty, I genuinely believe one will eventually come to a place where they might address their own underlying antisemitic hatred; not necessarily intentionally, but it may be skewing your thinking and ideas to some degree in certain respects. Professor Martin may have been a talented and intelligent professor in many ways, but in my view, he violated his duties as an educator when he chose to present tenuous information that had elsewhere been disproven in a concerted attempt to smear Jewish people rather than provide an unbiased, unhateful representation of historical events he was supposed to be teaching. No one benefits when curriculum and ultimately students are imbued with hatred.
