I agree with some of what you say but I'll refocus a bit.

The chem trails one is a good example of one of these that is going through this PR pattern I mentioned. Used to be it isn't happening. Now there's some defending of it because we've got to reflect sunlight to prevent global warming. It's mostly at the academic and the start-up level that "chem-trails" are being talked about publicly these days and it's not called that of course. Stratospheric Aerosol Injection, cloud seeding, geo-engineering are some terms that are used. Since you mention Vietnam: Operation Popeye is actually one of those operations declassified thanks to the Church Committee IIRC. In any case that was a case of chem-trailing to initiate rainfall for tactical reasons. Silver-iodide and lead-iodide were used in that case IIRC.

I'm using the word chem-trails provocatively of course. But I think we owe it to these people to say "Yes you guys were onto to something. I still don't think it is what you said it is but there are things going on which I denied. Stuff was and is and is indeed planned to be sprayed in the atmosphere and it has happened multiple times in the past. I was ignorant about that and thanks for bringing that to my attention." That's probably a good way to engage "chem-trail people" to start a discussion. That's how I've generally done it.

I'm also glad you mentioned cars. We all know there's additives in car fuel. And that lead used to be one of those and that it was a bad idea. There's additives in jet fuel also to keep it more stable. There's lots of jet fuel burned with so many planes flying daily and so many additives. Chem-trailing does happen on a pretty large scale just as a side-effect of safety precautions with regard to keeping jet fuel stable at high altitudes.

I generally like to steelman the side I'm arguing, and to argue with the best version of their argument I can think of. I've had to admit quite a bit of ground to the conspiracy guys in recent years. It does take some curiosity, good will and intellectual honesty.

Since you mention false memories. That reminds me of another one of the declassified CIA ops. MK-Ultra. There were a bunch of other MK programs too. Wouldn't surprise me if CIA experimented on this phenomenon this on unwitting suspects in the MK-Ultra operation or one of the other MK ones. Some pretty crazy stuff about these programs is declassified. I haven't read through all of it but their experiments involved tings like dosing unwitting subjects with LSD to give you a sense.

A critical thinker with basic knowledge of history and human nature will not exclude conspiracy. It can be uncomfortable to think about. It's an interesting question whether we should give benefit of doubt or do the opposite as a default setting. Some dangerous possibilities arise if politicians, government bureaucrats, media, academia and business people collude or conspire. It'd be pretty hard to stop them. We'd have to hope what are up to is a good thing. And hope is not a strategy. It's probably a good idea to err on the side of too much transparency, skepticism, critical thinking there.

I often see people bend over backwards to exclude any possibility of a conspiracy going on. That seems to be the automatic reflex of many people. No social media big tech is not conspiring with government to censor and ignore the first amendment. No big pharma was not colluding with government to change laws and recommendations. No big food is not colluding with government to change the food guidelines and subsidies. No the arms manufacturers are not colluding with government to instigate wars or prolong them when diplomacy would be best for the common good. All these things happen for the best and noblest of reasons even though the revolving door phenomenon between industry and government is in plain view for all to see. Of course Bill Gates is a Philanthropist and not a megalomaniacal monopolist even though he increased his net work though his philanthropic work. Etc. I actually like my journalists to be skeptical and to not be afraid to call out conspiracies or theorize about them.

There is utility and even some rationality in acting as though there was or could be conspiracy everywhere. It will cause the person to research and question differently in a way that conspiracy will be discovered in cases where it never would have been discovered if the suspicious attitude were not there, much less if the opposite is there. Of course there is the possibility of seeing conspiracy where there isn't any. I do think that's most often a safer situation than not seeing conspiracy where there actually is one. I am grateful these conspiratorial thinkers are out there. I think they serve an important role. I don't think ridiculing them is a good idea. I think we should engage with them from an attitude of curiosity. We might learn a thing or two from some of them.

I should have mentioned more concrete cases in the previous comment. I'll add some here in addition to the ones already mentioned. CIA has a rich history since WW2 of "spreading democracy" or "protecting" it via funding protest movements and instigating overthrows / coup d'etats. Lindsey O'Rourke's book "Covert Regime Change" documents some of these. The most relevant recent example of this is Ukraine in 2014. People will call that a conspiracy theory but as it happens that is conspiracy fact and the perpetrators, like Victoria Nuland admit to it (just like the CIA itself admitted it was engaged in and orchestrated all these conspiracies in previous decades, in that case they were forced to open the books through legal procedures during the Church Committee). These are not up for debate. That's not "Russian disinformation". Soon the constitution of the USA will be called "Russian disinformation" and the USA founding fathers plants of the Kremlin... So ridiculous yet so many believe the talking heads on the tube. Operation Mockingbird is an interesting one of these declassified CIA operations to look at in this context. Of course such things could never ever be going on today... Let's not even consider that as a possibility, right?

I like to refocus the discussion to these sorts of real conspiracies. Just because there's whacky conspiracies many of which wouldn't even matter much even if they were true does not mean you should focus on those exclusively. That's why I felt the need to write these comments: to refocus discussion to admitted conspiracies (e.g. admitted by the perpetrators in the case of the 2014 maidan coup) and those with a higher level of plausibility and importance.

If you'd like me to elaborate on any of these things I'd be happy to try. I've got a cursory knowledge on many of these things but it's not that deep. If you're gonna research it yourself it's probably a good idea to use search engines like yandex and startpage in addition to whatever one you're using. Definitely don't use google alone.