I think the El Dorado arc muddles the waters pretty hard on if they are capable of actually choosing to be as evil as they are. Like, Macht desperately wanted to understand human concepts of morality and justice and was physically unable to despite decades of trying.

It keeps getting shown that they aren't really capable of understanding things that seem obvious, like "what calling for help means" which they only grasp on the level of "lures prey easily." What to us makes them horrific and evil seems to be just baked into their genes, including the fun element (much like a cat toys with its prey in real life despite it being a simple animal).

This doesn't change the fact that they are incompatible with all things and deserve to be destroyed a tall times, however.