Had this been an episode of TNG, that is what would have happened. After some boring technobabble, the creature would apologize and promise to be a good little monster and not eat any more innocent space travellers who happened along (don't get me wrong, TNG was a good show, but it could get very preachy at times).
The Alphans did not have the time or resources to take a chance like that. It was kill or be killed.
Agree on all points.