Well, smart people usually try to base their opinions on specific information instead of pulling things out of their ass. A whistleblower revealing information.

Well, smart people usually try to base their opinions on specific information instead of pulling things out of their ass. A whistleblower revealing information. Internal documents laying out a strategy, or even a desire, to conspire. Something that leads one to conclude that a conspiracy is taking place. In the absence of such information, it's just making something up, or in other words, complete bullshit. So asking for a source is trying to give that person the benefit of the doubt that they aren't just a conspiracy theorist and that they might actually have a good reason for believing what they just said.