Unfortunately, separating out our biases from the objective reality is excruciatingly difficult. This is why I prize, at least, personal congruency through development of character and a true desire to remove bias, which I believe leads to right action and thought.
Regarding this article: The word "evil" is like a "catch-all" bucket. Some regard it as an untouchable absolute. Some suppose that it ought to be an untouchable absolute and that evils cannot be compared. This comes with the side effect that "evil" is parasitic--if something is in any way related to an "evil," it becomes contaminated.
I know that when I make contentious claims in ethics, I try to start from assumptions or goals that many of us can agree upon if at all possible--or, at least, I give some thought to the broader context. That way, at the very least, we all know that we're working toward similar goals, and the ideas themselves have less of a chance of being seen as viscerally "wrong" or threatening. Sometimes, I start with very general things, such as "we want negative ethical consequences to be reduced." Then, if others see something that is wrong with a methodology that I propose, perhaps they will see that it just needs a slight tweaking rather than that it's starting from "evil" assumptions.
I believe that, since these authors haven't started with what exactly they are trying to accomplish, their motivations are doubted, and their entire work winds up being cast aside--no matter how logically sound it is.
It's just how we work; especially on ethical issues, we'll wonder whether or not there's an agenda.