[msla]

Another definition:

A conspiracy theory is an explanation for an event or situation that invokes a conspiracy by sinister and powerful groups, often political in motivation, when other explanations are more probable.

[seph-reed]

You're defining a bad conspiracy theory. Most (but not all) of them are bad. Some of them have been true.

To say all conspiracy theories are bad is to say the government never conspires, or at least nobody ever correctly theorizes about it. Seems unlikely.

[msla]

No, I'm simply using the noun phrase the way normal people use it:

https://en.wikipedia.org/wiki/Conspiracy_theory

and check out the citations.