Does Matt believe people are inherently evil or inherently good? My fiancé and his best friend were both raised Christian and got into a heated debate about this. I know what I think Matt would pick but I don’t know if it fits his Catholic upbringing…
I'm pretty bummed that the Catholic-ification of Matt Murdock is leading people to ask these kinds of questions about him (not your fault; it is what it is). The Matt that I know exists in a world of nuance and shades of grey, and to me, that's part of what makes him fun! I don't consider myself an expert on Catholic Matt as a character (in my defense, he's pretty new), and not being Catholic myself, I don't have an understanding of the theological nuances that would likely be needed to answer this question in a meaningful way. But what I can say is that at his most devoutly religious--which was probably in the Zdarsky/Checchetto run, at least so far--Matt was very vocal about his belief in the importance of offering supervillains chances at redemption.
For most of his history, again, Matt has thrived in the realm of nuance and hasn't really been playing around with concepts of "good and evil" in a theological sense*. He is far more concerned with the dichotomy of innocence versus guilt, centered on a person's choices and behavior rather than anything inherent. As a defense lawyer, he believes that everyone deserves their day in court, and he is passionate about defending the innocent, but he will also never hesitate to use his superpowers and advantages as Daredevil to determine extrajudicially if someone is guilty. He believes in punishment for criminals as one of the foundational pillars of his life's work, as both a lawyer and a superhero. He does occasionally refer to people as evil, especially when it comes to his most dangerous enemies, like the Kingpin and Bullseye--if someone is repeatedly murdering your loved ones and destroying your life, you're gonna start calling them names. There are people who Matt considers pretty damn close to irredeemable, and we have seen him, in his darkest moments, decide that death is the best way of handling one of his enemies because they are just never going to be a good person. But again, it is an evilness tied to behavior, and we're talking extreme cases, here. We're talking Matt attempting to beat the Kingpin to death on several occasions. We're talking Bullseye remorselessly killing over and over again, driving Matt to snap and gut him on the roof of the Javits Center.
And at the same time, there's Matt's ongoing moral conflict with the Punisher, centered on his (Matt's) core belief that committing a crime does not make a person deserving of execution. Back when Rachel Cole Alves was attempting to join Frank Castle on his mission, Matt desperately tried to push her away from going down that dark road because he knew she was capable of making a different choice if given a good enough reason to do so. There's the much-praised issue "Roulette" (Daredevil volume 1 #191), which ends with Matt deciding: "Yes, Bullseye is a terrible person, but who am I to judge him? I'm not great either."
Daredevil vol. 1 #191 by Frank Miller, Terry Austin, Lynn Varley, and Joe Rosen
In some versions of Matt's origin story, his father was strong-armed into working as a mob enforcer for a while, which didn't change Matt's idolization of Jack as being fundamentally a good man. Matt is also friends (sometimes) with Melvin Potter, the Gladiator--originally a guy who shot spinning blades at people for fun, but who Matt has seen work very hard to temper his violent urges and become a gentle, loving person. Matt knows that good people do bad things in desperate situations and that bad people are capable of choosing to do good, and that in the end, we're all messy and screwed up and influenced by the people around us, by forces beyond our control, and by the world in which we live.
So if I had to pick one, I'd say that Matt thinks people are inherently good, but that still doesn't strike me as a fair or accurate representation of his attitude toward the world. He has witnessed firsthand the degree to which people are capable of great good or great evil. Matt can be a judgmental bastard to even his closest friends, and that's part of his charm, but it has nothing to do with any inherent traits of humanity. It's "You made a bad choice. Do better." Or it's "You did harm, so I'm going to kick you in the face." Regardless of anything Matt may have been taught in church as a child, as an adult, he isn't approaching his attitude toward people in a cosmic manner. He is too deeply embedded in the down-and-dirty complexities of ordinary life.
This is not at all meant as a dig at your fiancé or his friend, but I think suggesting that such a morally complex character would see the world through a purely black-and-white, good-versus-evil lens one way or the other suggests a slight lack of core knowledge about Matt Murdock. (Which is okay! That's what me and my obsessive back-issue reading are here for.)
*Of course, the Marvel Universe contains beings that can be classified as inherently evil, in the traditional sense of the word. Matt has battled Mephisto, the Beast (the Hand's patron demon), and other demons and their minions, and in that context, the theological connotation of evil is a concept that Matt confronts as a cosmic truth. But obviously, that's a very specific type of situation.