Have you ever seen an atom? Have you ever had access to a Scanning Electron Microscope or equivalently advanced machinery to observe one? If not, you have had to put at least some level of faith in that they do exist.
It is perfectly rational to believe X in this scenario even if I didn't test all of it myself.
I don't trust people who claim Y, get angry whenever I try to test any part of Y, the few things I test about Y aren't true, the people I know who tested other things about Y also saw that they weren't true.
It is perfectly rational to assume that Y is just nonsense in this scenario even if I didn't test all of it myself.