Your contacts taken a nasty pasting from some gangers it looks like his spinal cord is damaged and he will never walk or use his arms again. When he comes to he begs your group to kill him, he clearly does not want to live like this.
you used the example of someone with a spinal cord injury as someone who "clearly does not want to live like this".
How have I misconstrued that?
You miscontrued it by ignoring the (now-)highlighted qualifier that the injured person, for whatever reason, is begging for death when he regains consciousness. Their choice as a plot device, not necessarily yours as a person.
So your character walks away from the sad, depressed chummer. On the positive side you've demonstrated to your fellow players the evils of ableism. On the opposite side, he's of no immediate use to you or your character anymore and as a player you will eventually forget all about the NPC.
Unfortunately, a HUGE aspect of the SR setting is that people are only worth the nuyen they can spend on or earn for others, and not a micropayment more. Maybe the gang members, maybe the NPC's loan shark, maybe the clinic itself, but someone's going to realize that the guy's still good for a few nuyen, delivered fresh to Tamanous, once the news is out that no one's watching. Or, maybe someone places a call, and the GM brings the paraplegic back as a "brain in a jar". Do you really think he's going to thank you for his new life?
This brings us back to the in-game ethics of what a "good guy" in this (deliberately dark for the purposes of example) setting might want to do, and the in-game mechanics of what that good guy might be able to do.
Let's leave the hypothetical paraplegic in his hospital bed for now.
In my current tabletop game, my character recently managed to save a few bystanders from an explosion. Not everyone, and by "save", it turns out that one PC now needed professional treatment to reduce the severity of the nightmares he now suffers. One NPC ended up with a (wiz!) bone armor/carapace in addition to his skeleton - we sent him off with a free spirit who was interested in him. Another NPC ended up with acidic(?) drool pouring out his mouth, burning his own clothes and skin away. My character opted for a 9mm dose of lead anesthetic in that case. "Good guy" or "Bad guy"?
I'd think there are any number of stories that can be told in a lighter setting and still be fun, and goodness or kindness need not be penalized. In a darker setting, or even one hitting too close to home IRL, clearly the GM and players need to establish which elements need to be left out.