Just one soldier released in exchange for 5 hardcore terrorists. These terrorists in turn will kill many more American soldiers. Bergdahl wasn't even a high ranking officer to begin with.
His rank isn't important there, the point Obama is trying to make is that he was a POW. And indeed, he was. So were the 5 Gitmo detainees. It was a POW exchange, nothing untoward about it.
Also, the Army is taking the stance that he is innocent until proven guilty with regard to the allegations that he went AWOL/deserted his post.
So until he's proven guilty, it's like you said: He's a POW.