> I'm pretty certain that a substantial percentage of the most ridiculous conspiracies are posted online by paid shills to discredit all theories, so any dissenter can be labeled a "loon".

So the “elite class” conspire together to craft fake conspiracies and flood the population with it so that they can label people who discover the real conspiracies as crazy?

You are bringing up the “elite class”. It could be foreign governments to create dissent. It could be Democrats to discredit a Republican forum or vice versa.

This is perfectly plausible. It's also intractable, and doesn't imply that we should believe more things, any more or less than it implies that we should disbelieve more things. No matter how much misdirection and falsehood is put out by whatever organized or unorganized bodies, we still only have what we see and hear and read and experience. It's just one more of a million obvious reasons we already have to be skeptical - skeptical of what we're told by authorities, but also skeptical of what we're told by any given person with any motivation to convince you of something: financial, political, or even just emotional, and that includes conspiracy theorists. But there's a balance - if you're too skeptical, then nothing has any meaning. You might as well not believe any information you receive, in which case you might as well become a hermit who lives off the land (which is fine, but not a realistic expectation for the whole world). Or, in the case of many conspiracy theorists, arbitrarily choose something to believe (arbitrary because their sources are not any more reliable than other sources), which really isn't any better.

So, we want to avoid falling off any given edge (becoming a hermit or a person with no opinions on anything, becoming a truly nutty conspiracy theorist, or becoming a mindless loyalist to some social/political group). A key tool for avoiding this is understanding a few things:

1. There is a bigger space than you think between having no opinion and having a full-blown conviction. I can believe or disbelieve something without making it into part of my identity or taking any kind of serious concrete action based on it or trying to convince everybody to go in the same direction as me.

2. It follows from #1 that it is OK to be wrong.

3. It follows from #1 that it is good to change opinions based on new information - it is not hypocritical.

>Yet people will still believe that 0% of theories are correct.

This is not a generous portrayal. The people you're talking about mostly believe things based on experience (e.g. evidence, though there are many other kinds of experience). Therefore, if their experience tells them something a person is insisting on is probably not true, well then that's their perfectly reasonable position at the time. That is not the same as having a conviction that any given thing is not true, and it is very much not the same as believing that "0%" of anything widely considered a "conspiracy theory" are true, for all cases, forever, as some kind of ridiculous rule.