It's his version of CYA...I'm sure deep down he thinks Obama is illegitimate but he don't want the goons to break down his door.
IMO that stance is what makes this guy believable, as far as what he thinks and knows to be correct.
Fact is, he does not realize that to be POTUS, you have to be natural born, which means two citizen parents and born in the USA. Obamas father is Kenyan and never ever because a US citizen, and died a subject of Great Britan. Under the constitution Obama does not qualify as a NBC, so cannot be POTUS per the constitution he has sworn to uphold.
I personally don’t even think his is a citizen at all.
Add to that he was adopted by Lolo Soetoro, so his name is Barry Soetoro, and he swore he never held any other name than Barak Hussien Obama. See, he lied again.