My point is just there is another level of control, not banning books but silencing or suppressing them (or pick some other term that fits better)
Anyone not previously familiar with suppression as it is practiced would be more readily swayed with something they can sink their teeth into and investigate. What you've given them instead are vague and unverifiable claims that, without elaboration, carry the hint of paranoid fancy rather than serious conspiracy(which risks unjust dismissal by someone could have otherwise been informed).
Let's use my first guess of Tragedy and Hope as an example. Consider the following:
-pedigree of Quigley: History professor at the Georgetown School of Foreign Service who taught Bill Clinton and an entire generation of diplomats
-contents of the book: macrohistorical view of Anglo-American governmental, financial and intellectual organizations and how they shaped history
-manner of its suppression: first editition pulled, subsequent editions published without the passages detailing the establishment of the BIS backed by private bankers and the existence of what Quigley called the "Round Table Groups"
These combine to paint a clear (and researchable) picture of what you alluded to: books not being banned, but having their impact diminished, because they challenge or critique the power structure.
I'm fairly certain your second example is Tragedy and Hope by Carroll Quigley, although he was an American teaching at Georgetown. Your first might be Dark Alliance by Gary Webb (if one defines "distributor" very loosely), but I haven't a clue on the last two. They don't trigger anything in memory and the details are too vague for a fruitful search. Be a good sport and elaborate.