Moon missions then...
You believe they happened?
Held a moon rock in your hand have you?
If so, how do you know it's genuine? Did you go and collect it yourself?
There's not a telescope in existence that can resolve the lander or the flag, so you can't look at them yourself.
All we have for evidence is photos, personal accounts and records - all of which could be faked...
All of the evidence is what various government agencies have chosen to release
Oh, much like whether there's an alien craft in storage...
(Personally, I use a balance of probability - the moon missions probably happened so I choose to accept they did. There's probably not an alien craft in storage.)