The kind of experts gojomo is thinking of are still resolutely convinced that they're correct, and no facts will change their mind about that. Like the people the tobacco lobby used to wheel out to tell you that they were confident smoking was actually not dangerous, or the same handful presented as offering an "alternative" explanation for global climate change, they are fiercely resistant to the obvious conclusion from the available facts, and I don't really need to care whether that's because they're they're actually paid not to look at the obvious or they're not smart enough to see it.
Not trickle down, but Laffer (the guy the Laffer curve is named after) worked for Donald Trump in his 2016 campaign, and currently blames Barack Obama for the Great Recession.
Laffer's curve is 100% real, it's also 100% irrelevant to real world economics. It's as though after explaining about relativity and why it's impossible to accelerate an object with mass to the speed of light, a physicist turned around and told you that therefore they are confident that it's impossible to move at more than a walking pace and so Olympic sprinters don't exist. And then an entire political party pretended to believe them because it would make very wealthy people even richer. The analogy breaks down there actually I guess. Also the part where loads of people die in miserable poverty, that's not really in the physicist analogy either.