From Wikipedia:
The Universal Declaration of Human Rights (UDHR) article 13 states that [...] everyone has the right to leave any country, including his own, and to return to his country.
It may be difficult to block you from returning (where would you go?) but it is much easier to prevent you from leaving ever again. It's still against the UDHR, but since they are issuing passports they are firmly in control. They can deny you a passport for several reasons already.
Not entirely true. A USC can show up with nothing, declare themselves a citizen and they have to be admitted. Obviously there will be a process involved in proving the claim but you must still be admitted. Even if this guy was a complete jackass, once it is determined he is a citizen he must be admitted. There are quick ways and slow ways to get through customs. This guy seems to relish the slow way.
I would bet that he wouldn't act like this if he had a tighter connection.