I can answer this. Firstly, this is not exclusive to video games, but extends to all other forms of media. In the real world, being violent or not has real world weight everyone feels and is learn/taught about because it is an element that we all deal with in this world. No matter who you are or who you spend time with, you'll encounter, learn, and form values on violence outside of video games.
If you grow up in a neighborhood surrounded by a specific type of person and not many examples of other types of people, your views on these people will stem from something else. For most it's media. Media propaganda exists because people are creatures who seek knowledge, and if not first-hand experience they can consume media to construct their views. In South Korea, they close out and super limit who's inside South Korea to form their opinions on people outside of Korea. They're taught that Americans, North Koreans and the like are the bad guys, and they're the superior race, and close out or super limit their exposure to anything that may contest these views.
In a more common non-South Korean example, media helps construct our image of things we lack exposure to. If you have spent a lot of time with a broad range of people who have disfigurations or disabilities, then the media involving this won't really influence your views because you have a lot of real world experience and exposure. But most don't have common interactions with a larger group of people with disfigurations or publicly perceived disabilities, and if you don't, how society and media treat a group of people will influence your behavoir towards that group of people and how your mind registers them.
So if media is almost always constructing bad tropes around these people, and they are very often depicted as the bad guys, then that does set a subconscious mental thing. It also establishes and instills an idea that people who have disfigurations are naturally less trustworthy because in media have physical deformities usually is a sign that your evil, or stupid, or crazy, though it's literally just a physical thing in most cases. This creates a stigma, and as this is something that's seen physically as it's only skin deep, it makes people treat you in the way they've been subconsciously taught by media.
The thing is, this trope is so common and prevalent that it 100% has real world affects. A casual example is someone might not let their child walk close to someone with a disfiguration compared to a "normal" person because media has instilled in them that this person could be a potential threat. They're not any more of a threat than anyone else, but the stigma is there due to media's portrayal of them.
On a further element how violence and this differ, violence is a physical act that you make a conscious decision on. It's something you have to enact and isn't something you keep in your head for the act of doing (you may think about doing something violently to someone, but if you don't act on it, then whatever). Meanwhile, having a stigma on a group of people is internalized, and the way you act on it is much easier to do since it's mostly being avoidant or having biases, which don't take as much precise action to act upon.
