"Conspire" means "breathe together" in Latin. Conspiracy is intimate. The conspirators are vulnerable to each other, open with their thoughts because they have common interests. The conspiracy must remain secret because it only serves those interests.
From this point of view conspiracies, and by extension conspiracy theories, are as natural as communication. Why then are people today reluctant to say, "I have a conspiracy theory"? 
Perhaps the rumors are true, that the CIA promoted a negative connotation for the phrase "conspiracy theory" to embarrass people who doubted the Warren Report on President Kennedy's assassination. If that conspiracy theory is true, it was stunningly successful. To say that someone has a conspiracy theory is to label them a nut.
It's interesting too that the word "paranoia" is understood by almost everyone while its opposite, "pronoia" (referring to denial that there are people conspiring against one when in fact there are) is mostly unknown.
Of course, even if someone overcomes the stigma of vocalizing a conspiracy theory, and even if everyone who hears the theory thinks it's true, you still face the question: What are you going to do about it? You can't take legal action because a conspiracy theory is a theory; it is not designed to be a formal allegation, as there is generally little or no evidence to back it up.
For instance, I have a conspiracy theory that Big Pharma is behind the move away from attributing significance to dreams, which are referred to in many medical journals as neural "trash" to be flushed down the toilet of sleep. My theory is that the downgrade occurred because there is no money in dreams, as there is in drugs. If dreams have meaning and are studied, as was the fashion in Freudian times (e.g. Beverly Hills, circa 1960), and if people are able to assuage life's problems by talking about dreams- as believed not only by Freud but by numerous human cultures- that's not good for a system in which mental health is addressed with prescription drugs, which means it's not good for stockholders.
The term "depression," too- in my conspiracy theory- has been co-opted by Big Pharma. In the past, a state of depression (previously melancholia) indicated that a person was "sad," a term that is avoided in the pharmaceutical world because we understand that sadness can be caused by the world outside the sad person, and there's no Rx for that. Today, the person is affected not by the outside world, but by chemical imbalances within. That's where the money is.
But what can I do with my conspiracy theory about Big Pharma other than blog about it? There's no legal action to be taken since I have no evidence, and because the pills often work, there's little hope of inspiring a pro-dream movement against medical science. People would ask: What have dreams done for me lately?
The only struggle for change I'm interested in is the struggle to reattach a neutral connotation to the phrase "conspiracy theory," so that if you laugh at my theory about Big Pharma nixing dreams, it will have to be because you can prove it isn't true, not because I can't prove it is true.
[Update, 8/1/26: I suggest a conspiracy theory regarding President Trump’s proposed executive action for a $1.7 billion “Anti-weaponization fund. ” The fund, as widely reported, could be used to pay the “January 6th” participants for their “pain and suffering.” That element alone is enough to inflame those opposed to Trump’s agenda, but look at every news story covering the proposal, whether print, network or cable, whether on the right like Fox News, or on the left like CNN and MSNBC, and you will find that the coverage emphasizes that the proposal is “taxpayer funded.” To call a proposed government action “taxpayer funded” puts the average reader on high alert that something crooked and destructive is coming. When the reader then learns about the possible January 6 pay-off, you have a recipe for unprecedented outrage. What political goal is at play here? There are clues: American news outlets, of all political stripes, do not normally recite the same descriptive phrase over and over, as they are with “taxpayer funded,” so a central directive to use the phrase is highly likely. What motive could explain a deliberate attempt to create intense opposition to a Trump proposal? Herein lies the conspiracy theory. Most Americans have noticed that whatever Trump wants, he gets, and this situation troubles Congress, especially as mid-terms approach. Both Republican and Democratic Congresspeople have stalled the Anti-weaponization fund, thereby appearing capable of resisting Trump. What they are really doing is engaging in theater. Trump never expected to succeed in creating the fund, the media was directed to ensure widespread opposition, and Congress can play the role of defender of the Constitution, just in time for the mid-terms.]