MK Ultra, Big Tobacco, Big Sugar.

These aren't conspiracy theories. They're well documented, exhaustively researched, and heavily reported upon programs and organizations.

The conspiracy theories came about as attempts to cover up the above. The Helter Skelter motivation, which then bled into increasingly lured claims about rock music being mind control and a race war prophecy were the conspiracy theories. These claims helped cover up MK Ultra as a project and deflected state effects at manipulating civilians onto mass media and The Culture War.

Similarly, it wasn't "Big Tobacco" that was the conspiracy, but the repeated denial-ism funded by tobacco corporations which sought to conflate restrictions on smoking with some kind of police state pogrom on the working class. The same game got played with asbestos and lead paint and motorcycle helmets and seat belts. Wave after wave of reactionary media funded by libertarian-aligned business interests tried to blame the victim or mystify the source of harm.

"Big Sugar" is a complete misnomer, as the shift to corn syrup over sugar was in direct response to the Cuban Revolution and the sudden shortfall in sugar supplies following the US embargo. That, again, wasn't any kind of conspiracy. But the increasingly aggressive sales tactics of soft drink salespeople certainly created misconceptions about their benefits and hazards.

And what’s the point of trying to dismiss all conspiracy theorists as racist lunatics?

Yes, why would anyone conflate eugenics, phrenology, and other pseudo-scientific claims of racial superiority, or the increasingly apocalyptic predictions of social collapse coming from segregationists and their business allies, might feed into conspiracy media.