I have said that conservatives have too much memory, liberals have too little. As an example, in the 2000 election, Al Gore's two main campaign issues, that he went to the mat over repeatedly, were that the environmental issue of global warming, just then beginning to be remarketed as climate change, was dire and needed emergency attention, and that he had more foreign policy experience than George Bush. Those are what were stressed at the time, so beware of history rewrites. I suppose you could ride unicorns through some fantasy of what Al Gore would have done differently after 9/11, following on a Clinton administration that insisted Hussein had a WMD program, but I personally will just nod politely and then leave. Other things you dislike about Iraq and Afghanistan - though likely also conveniently edited in your memory and refutable if I wanted to bother to go pull some contemporary articles - are irrelevant, even if you could prove your case. The Republicans now win the intellectual argument from 2000, hands down. (BTW, I think they would do that for most elections in my lifetime. Honest hindsight favors them. I readily acknowledge that the unknown factors that pop up in any presidency are usually more important, and who would prove better once those unknowns are known is always going to be much more debatable. That's fair.)
I use that as a lesser example of other events that should be yuge in memory but are buried now. The collapse of the Soviet Union and the information that then poured out, verifying the anti-communist, even the nutcase anticommunist accusations is one of, if not the most important political fact of the 20th C. Liberals had a hard time burying that completely, but they are skilled, and some are shameless (you nice liberals have not done much to enforce against the shameless ones, frankly), and now you don't see much discussion of that in The Nation, or The New Republic, or on Vox/Slate/HuffPo. I mean, it was only the most important event of the century, right? Let's talk about ten years of Nazis instead, and insist that all your neighbors who vote conservative are just one step off that.
In specific, there is Alger Hiss, accused by Whitaker Chambers of being a Soviet spy. The intelligentsia divided in the 50s over the issue, and the fact that he was prosecuted by Richard Nixon caused the left to hate Milhous forever. While he was president he did become increasingly paranoid. But if you look back over the data and subsequent events and realise he was right and they were wrong, but look at what they asserted, you might see why. That would be a good simple time-travel intervention in early 1972, actually. Dick, chill out. You win in a landslide, no need to try to drive every nail to the center of the earth. Back off a notch and no secret maneuvers at the Watergate Hotel, capisce? Don't overreact here because of what you hear in DC. The rest of the country isn't Washington. Though maybe that is me riding unicorns. People can't back off from who they are that easily.
Even when I was in college in the 70s, and on through the debate in the 80s, all the Real Intellectuals assured us that it was all witch-hunt, that Hiss was merely this nice Quaker man who was a liberal and only wanted good for all mankind. Subsequent information has vindicated Chambers and Nixon, not Hiss. The recent issue that Wikipedia is not merely a bit left-leaning in its view but seriously slanted on socialism/communism issues in particular has a great test case here. If you read the article on Hiss superficially you could well conclude that this is all still pretty debatable, favoring the idea of his guilt but not fully establishing it. Yet if you look closely line by line at what is solid and what is "wait, there is still a possible escape door," you see that the debate is closed. He was a Soviet spy, and the best his defenders can muster is that he might not have been all that important, so the damning archives are scant. The parallel case was the Rosenbergs, which also eventually went down ignominiously, with their best friend eventually admitting well, yeah, they actually did pass secret information to the Soviets.
This is in retrospect devastating to the assertions of the liberals of the 1940s, the 1950s, the 60's, 70s, 80s, and 90s. Along about that time, all but the few true believers decided that the new line would be that it isn't important. It's old news. It happened so long ago. Who cares? It doesn't matter now.
So how important is it, now that only one of my five sons is likely to have even the merest idea what this issue is? Does it matter that the largest, go-to-the-mat assertions of liberals from 1940-2010 have gone down in flames? I tried to find a very contemporary equivalent and thought of James Comey. Put aside what you currently believe about this William & Mary College visiting lecturer on Ethics, and consider that long view, if we could bring back from thirty years in the future all the internal department investigations, all the deathbed confessions, all the documents people thought were destroyed but were discovered, all the later behavior of the participants. If all the evidence of the next thirty years moved inexorably in the direction that Comey was on to something not visible at the time, and made reasonable interventions in service of the republic, that would matter. It would in fact be devastating to the Trump claims. OTOH, if the next thirty years showed the opposite, that the FBI knew but buried info, that procedures were not just skirted but intentionally ignored with the vilest of justification, etc would that not be devastating to Trump's opponents? Consider both sides. Consider what the honorable thing would be for you to say in 2046 when a great deal more is known.
While you are considering that, remember that this has happened twice already, with Hiss and the Rosenbergs. But my memory is long, and who under the age of 60 cares in the slightest?