@Walter Hinteler,
Correction: those he
allegedly met.
That's the thing with Yoyo: you can give him whatever evidence you want, he will always make them mean what he wants to think. So if a Mirage pilot wrote that he loved the aircraft, Yoyo thinks " what else can he say in a government report; of course he will say that to please his superiors..."
That pattern of thought is important because all deniers use it repeatedly and without any bound. E.g. "of course climate scientists are going to conclude to climate change, because they want more funding"... etc. etc.
The difficulty here is that there is no observation whatsoever that does not require a degree of interpretation and bias analysis. Interpretation is always required. One may or may not trust certain data, given how it is collected, etc. The problem with the deniers is that they are incapable of interpreting ANY DATA WHATSOEVER in a way that will contradict their preconceived opinion... Therefore, their opinions are not falsifiable, and they can live in their own little universe, isolated from facts.