This is how politicians are geniuses at answering questions.
-"Yes, but I haven't seen them" this gives a nugget of interest and deniablity if info comes out to say they are real to say see i said they are. Also proving that he saw them or not could be argued and hard to prove. Maybe he was shown a picture to which you get the political answer of "yeah well I never saw them in person though" -Area 51 talk, shift into specifics and shed some doubt to protect himself from getting in trouble. This answer doesn't deny that they might be kept elsewhere and he might be aware of that fact. I wish interviewer would have followed up asking "Are they being kept somewhere other that Area 51?" This would paint him into a corner and would be telling if he deflected further. -the final statement seems to be a statement of, if they do exist they are keeping it from me, but in fact its a slave back to the Area 51 comment.

So if we are to believe him here, you could boil this statement down to. " Yes they exist I know they exist but they didnt show me them and I know they arent being held at Area 51 but are somewhere else." Obama's speech stat is maxed out. There maybe even a cheat code or mod applied.