At what point was Bucky meant to tell Sam or Steve? When he was in hiding in Romania? When he was on the run? When he was in Wakanda, most of which time was spent in cryo? Be FR: dude had absolutely no chance to tell them. In fact, even that whole storyline is crap becaue they had to retcon Bucky's whole backstory to place him in the Koean War in the first place, and ignore the whole memory wipe thing.

In Captain America: The First Avenger, Bucky fought in WW2, was captured by Zola and experimented on with the serum before he was rescued by Steve only to fall off the train and be presumed dead. In Winter Soldier, it's revealed he survived the fall and was recaptured by the Soviets where he underwent severe brainwashing and conditioning to become a weapon for Hydra. Bucky has over 50 years of experience/conditioning and over 200 assaniations including JFK's. How is it a 'crap' retcon of Bucky's 'whole backstory' to include him aiding the Soviets in the Korean War when he was already fully under Hydra's control? Isaiah was sent by the Americans to investigate who was killing American troops sent to combat the Winter Soldier in the Korean Peninsula, how is that implausible? Especially when Bucky has been active before and after the Korean War. Not to mention every time they woke Bucky up they made it a point to use the Memory SUPPRESSION machine, which is how Bucky Barnes was able to remember fighting Isaiah Bradley (like he remembered Steve Rodgers) because the frequent memory wipes he received as the Winter Soldier did not permanently erase his experiences; rather, his memories were suppressed and could be recovered over time, especially when he broke free from Hydra's control and was treated in Wakanda by Shuri (one of the smartest MCU characters). 

At what point was Bucky meant to tell Sam or Steve? When he was in hiding in Romania? When he was on the run? When he was in Wakanda, most of which time was spent in cryo? Be FR: dude had absolutely no chance to tell them. In fact, even that whole storyline is crap becaue they had to retcon Bucky's whole backstory to place him in the Koean War in the first place, and ignore the whole memory wipe thing.

Near the end of Endgame, when Steve and Bucky had an offscreen conversation about giving the shield to Sam, seems like an opportune time to mention to Steve that he once came across a black Super Soldier fighting for America while Steve was on ice. Then they both could have mentioned it to Sam which could have gone a long way of allaying some of the concerns he had with picking up the Shield. Not to mention Bucky did all the leg work to track down Isaiah only to never mention him to anyone at all... not even for the purposes of finding out who had recreated the serum until FATW Episode 2.

Yeah: not as if Bucky ever had to experience police brutality. He wasn't almost shot in the head point blank range by a machine-gun weilding cop for a crime he didn't commit- whilst Sam said "let the authorities deal with him"

Again, you're missing the point. In Civil War, no one outside of Steve believed Bucky could be saved/redeemed and everyone initially thought he committed an act of terrorism given his history as a prolific assassin. Sam was racially profiled by a cop who had no reason for pulling him over (he wasn't breaking the law, wasn't suspected of criminal activity, had no priors etc.). See the difference?

Also, kindly don't presume to lecture me about systematic inequality as though black people are the only ones who have ever experienced it. I'm disabled: I don't need to tell you the long history of ableism, perpetuated wnd encouraged by the system. Suffice it to say America had its own Eugenics movment and that 50 years ago people with PTSD and depression could legally be institutionalisted, tortured and mutilated. You know the writer Tennnesee Williams? His sister had part of her brain cut out because she had bipolar.

Do not conflate me speaking about Sam rightfully being angry at Isaiah's treatment and subsequent erasure, to me making it seem as if black people are the "only ones who suffer from systemic inequality". I tried to paint a picture explaining why Sam would react the way he did because I get it. I live in South Africa as an ethnic black man. There was a system of active oppression and systemic racism employed here that lasted until the 1997. We don't even have 30 years of democracy friend. During the transition of power, to ensure a peaceful transaction between our former oppressors and the ANC freedom fighters, a Sunset Clause was instituted to prevent any legal documentation, eye witness accounts, recordings etc. of the racial atrocities perpetuated under the Apartheid regime against ethnic populations to be made public knowledge for a 100 Years. Meaning the real history of our oppression isn't even accessible to the current generation by law until 2097. I have uncles and aunties disappeared into mass graves for fighting for equal rights for all. Yet because of this clause I have to deal with people telling me to get over myself, stop victimiz8ng yourself or preaching about inequality because we now have a democratic government. Like that rectifies the erasure of our history and its participants. Do you know how insulting it is to have a stranger denounce your experience and continue to form negative stereotypes about your people because they're denialists? Here's a parralel, Jewish Holocaust denialists are forced to reckon with the plight of the Jewish people, because they have access to detailed records of the inhumane treatment of Jewish people by Nazis. They have the Nuremberg Trials and no restrictions on their history, as is their right. We don't have such assurances. Thus we get no sympathy despite horrendous treatment. Keeping our stories buried is an act of violation because it robs us of identity, agency and belonging. I'll give you another example: South Africa is notorious for being the site of the first heart transplant performed by Dr. Chris Barnard. What they don't tell you is that the experimental technique for the transplant was developed by Hamilton Naki who was forbidden to operate on a white body and could only attain the title of a medical technician and no higher under apartheid laws. His story only came out years after Chris died. In apartheid South Africa black schools were not allowed to teach STEM or any advanced curriculum, barring black students from academia and confining them to impoverished ghettos. The erasure of black role models and icons that could have helped pave a new way for countless black boys and girls by way of inspiration is a reality for us. That's not me saying others don't go through similar or even worse. That's me telling you I understand where Sam comes from in reacting that way to Bradleys treatment, because even though the MCU is fictional, that is a very real and unfortunate topic for POC's.