That statement in particular isn't what's crazy, of course various people of the elite strata will work and socialize and collaborate together to various extents.

The craziness is the specifics of certain conspiracy theories. For example the idea that covid itself is a conspiracy, or the there is a conspiracy to suppress ivermectin.

I have to agree with the view that outlandish conspiracy thinking isn't only wrong, it is actively dangerous and should be argued against strenuously. It was a large part of Nazi propaganda that motivated a genocide, so that is an existence proof of a danger associated with such unhinged thinking if it's allowed to go unchallenged in public discourse.

Because they're rich and powerful and its easier to belittle people with genuine concerns and with some incomplete evidence than it is to answer questions that might threaten their rich and powerfulness. And because there are a few who take their theories to extremes without evidence, its easy to lump all together with the crazies and demean them.