I don't want to be "that" guy and i'm going to get flack for this but there is a key difference between understanding a scene and understanding the idea of a scene. I think this is the issue towards the reception of the "Martha scene" and Batman's redemption in general in BvS
I think everybody understands the overall basic idea of the scene but it baffles me how you can say you understand the scene and then still proceed to ask "but why does he still kill after the martha scene". The answer is simple, you're not looking hard enough.
Snyder uses the cinematic medium to its full capacity. Everything you need to know about Batman's redemption is in the imagery and subtle motifs throughout the film but you aren't gonna notice this if you approach the film in a more literal sense.
I'm not trying to insult anyone's intelligence here. I don't believe that BvS is this hard to understand misunderstood masterpiece, hell it's far from it but i also don't think it's this dumb film either. I'm only trying to encourage people to merely approach it differently
And i'm not gonna lie and say that i've always liked it, i absolutely hated it when it came out. And of course there are some who are gonna label me a snyder shill, which i'm not. I absolutely hate Watchmen with a passion and i could couldn't care less for his non-DC films tbh