voting present should NOT be an option!!! that’s NOT why you were sent there...
You raise an interesting point.
Voting "present" is a form of non-representation, the opposite of his job description, and in the absence of an explanation could certainly be an affront to his constituents.
OTOH, the appropriateness of a "present" vote has long been recognized where it would be strategically important to a politician. I.e., congressmen and senators reserve the right to "weasel" out of an uncomfortable position.
But you and I don't think in this instance it was even a close call. The voting member should vote for what seems right or in the best interests of the body or the nation and follow that immediately with an explanation to his or her constituents, if needed.