You believe that because that is what you want to believe. His birth parents could be found, a US birth certificate could be produced and you still wouldn't believe it.
To quote Tom Cruise questioning Jack Nicholson in “A Few Good Men”, “I want the Truth”. You are apparently being Nicholson saying “You can’t handle the Truth” (just before he is marched off to the brig).
What I really want is a media who isn’t covering up a possible, or logical, immigration status of a sick mass-murderer because it has impact at a critical time for that particular element of public policy.
Of course, wanting straight, non-ideological investigative reporting out of the fake newsers is a pipe dream. I will believe information that deserves belief after some poking and probing, if/when it makes it into the sunlight.