Most Helpful Guy
If they actually exist then more than likely both possibilities of mermaids are possible.
They have similarities to us just for being half fish and not merely just animals. So more than likely they can and would be capable of both good and evil, and the choice of either is entirely on them.
Whereas to animals and fish I view them entirely as "neutral" and because of "Survival Of the Fittest" and the "Food Chain" animals NEED to eat and slaughter each other just in order to survive, and only the strongest, quickest, fiercest and most intelligent of them comes out on top and have the best chance of survival. There is really no right or wrong when it comes to that. Or maybe it can be viewed as "Might IS Right".1