And the difference is your mate had a pretty obvious reason to lie. What reason do hundreds of astronauts over a span of around 60 years and a handful of space tourists have for lying? The space tourists in particular, even if you think that astronauts are recruited to part of some conspiracy, what stake to space tourists have in this?
Prestige and politics.
Look at the history of space travel. It literally began as one-upmanship, US vs Russia propaganda. Let's suppose that this field they'd pinned so much hope of proving their superiority turned out to be something that was actually impossible, that each and every attempt they had failed. Would they give up, would they keep throwing money away, especially given they'd see rumours their rivals were going to succeed?
No, they'd lie. Create a huge patriotic fervour, get the reputation boost, play politics. Russia pulled off a magic trick and said they went into space, the US found a way to one-up that with "Oh yeah? Well we went to the moon!"
By this point it's become borderline nationalistic. Space travel began as a way to establish a country's superiority, and even now it gets wrapped up in that same passion. No honest discussion for people that try to debate it, just blind dislike and mocking. No one dared question it at the time of the cold war, and so it sunk into the public consciousness, got treated as real so much that people just refuse to question. Too late to back out and admit to the lie now, especially with the money that gets funneled into space agencies that they can funnel away into private accounts and slush funds.
Plus space tourists get prestige, bragging rights, you name it.
Honestly it's really not that bigger deal. Any administrator with half a brain could spin things so that tourists or, hell, I could make an argument for bloody Armstrong not knowing space travel is fake. Just comes down to the story you tell. Make it so they don't think they're keeping that much of a secret and who cares?