I think there is no evidence. Witness testimony is not it itself sufficient evidence to convict someone of a crime, why should it be enough to convince you that physics-defying aliens exist in the universe and somehow, for some reason, came all the way across the galaxy/universe/whatever to.. what.. fly around and make pretty patterns in the sky?

Do I believe there is other intelligent life in the universe? Yes, statistics alone suggests there should be.

Do I believe it's making crop circles and buzzing F-18s for giggles? Almost certainly not.

Do I believe some guy saw absolute incontrovertible proof that aliens exist and somehow both failed to acquire any of it to present to the world and failed to be credible enough to be arrested or otherwise silenced by the people who care a whole lot about the leaking of classified info? Absolutely not, not under any circumstances.

If aliens exist and are here and you've seen them then the best advice I can give you is next time grab a fucking button off a control panel, a blood sample, a piece of metal we don't know how to make, like literally anything, because we've been drowning in bullshit witness testimony on this subject for most of a century now. I don't care how credible you are, If 99.99+% of people who talk about aliens are crazy/hoaxers/attention-seekers/etc, the odds are pretty good you're not the <0.01% who is totally legit. So without some actual, physical evidence I'm going to go ahead and assume that you're a crackpot regardless of your credentials.