See now the only problem I have with nay sayers is these things have been being spotted for as far back as man has been recording things.
For me I think they are out there simply because too many have been being spotted for too long for there not to be anything to it.
And given the age of the universe its not unreasonable to think that there have been civilizations on other worlds have have existed become FAR more advanced then ours and have long since died out many times over before we ever showed up on this planet
Now can I absolutely prove they exist, No
But nor has anyone been able to absolutely prove they dont