IRL, A lot of atrocities were commited for the sake of medical knowledge, countless people were cut open and experimented upon and they all died. Would you classify the medical teams in charge of said operations as "evil"? Of course society would gladly hate upon them, though society has no qualms in using their research and letting them go scot-free for it.
Those who performed it were evil, yes. Those who used the research, unless they were also the ones performing it or allowing it to be performed, were not. I don't personally believe in the idea of tainted knowledge, though I do note the risks of allowing people to think that such means for seeking knowledge would be acceptable or fruitful.
This is because our society is built on hypocrites, our foundation is built upon countless bodies and we'll gladly compromise "ourselves" to attain such research, as long as we're not the ones doing the atrocities ourselves. We need those who are "inhumane" so we can keep our so-called "humanity" for ourselves.
Our foundation is built upon countless bodies because evil is more common the further back in time we go. We use the fruits of evil because we can't turn back the clock, nothing more. Eventually, I hope we can purge it from the human mind forever.
Cerberus represents this in the Mass Effect universe, their research being radical but evolving humanity's place in the galaxy and strengthening it's grip. Without Cerberus, there is no humanity, there's simply another puppet for the Council.
And like all evil forces, while its knowledge may be used, it must be destroyed.
Greatest net positive? What is the greatest net positive? Is it unifying countries through a series of well-propagaded falsehoods aka social engineering? Is it destroying those that exist simply to harm others? Is it strenghtening international trade to keep money flowing? Is it taking steps to isolate yourself to some extent to keep jobs within your borders? And so forth.
That which will lead to the greatest possible amount of pleasure for the greatest possible number of beings that can experience it, over the greatest possible period of time. We need to find out what that is.
You could argue religion is far more tangible than any of us. They've been around for a long time and will continue to be, where you are very temporary.. So, if I harmed someone to defend you, I'd be evil as you are largely intangible, a mere breath in the space of time. Enjoyment is also intangible? Cmon. Whether or not you can touch and feel something does not make it any less real or worthy a cause. Also, what is harm? What are the priorities when in comes to choosing where the harm should go? Why do people act like it's not inevitable to a certain extent?
In terms of tangibility, I'm referring to intangibles as things other than survival and that which is necessary for survival, for oneself or others. To do harm otherwise is evil to a greater or lesser extent. As for harm... the priorities are doing the least harm possible, with it being a better option to do lesser harm to more people than a great deal of harm to fewer (it's better to inconvenience a thousand people than to kill one).