One definition of 出来る is “for a person to have a particular nature.”
よう here is basically the same as ように would be, but に is sometimes dropped. It turns what came before it into an adverbial clause that can be connected to 出来る.
The basic structure is 人間は [このように] 出来ている, where [このように] is the part describing their nature.
So this is something along the lines of “humans have a tendency / predisposition to look more at the strengths, rather than the weaknesses, of people they don’t outright hate.”
I chopped off the translation at the part where it talks about how that is something that has been shown through psychological experiments, to focus on what the question was about.