It's about the integrity of the mayor and the fact he has demonstrated a lack there of. We require these people for their ability to exercise good judgement. They fail to demonstrate good judgement, they go.
The media isn't to blame for exposing this. If the media had said something that wasn't true Brown could have denied it and if needed take legal action.
Giving or receiving gifts isn't wrong for politicians, knowingly deceiving those empowered to enforce the rules is. Saying 'there is a lack of clarity' is a weak defence and basically a half hearted way of saying "I knew what I was doing was wrong and I didn't think I'd get caught".
We know why he wasn't declaring the hotel room use, he knows why he wasn't declaring the hotel room use. That anybody who knew what was going on could hold a secret like that over the Auckland mayor is an unacceptable risk.
That Brown put himself in that position is an unacceptable lack of judgement.