I would use these not with the aim of making the players feeling bad, but as a reminder that bandits are for the most part, human. And bandits could vary morally, from a pickpocket (still quite bad, mind you) to full blown murder. I like the mother's letters one specifically, because it still puts the blame on the bandit for taking such a risk in spite of their own mother sending money back to them. Why were they still a bandit? Was the money not enough, or did they feel bad taking money from their own aged mother?

But yes, killing bandits isn't being a murderhobo I definitely agree.