There is a sense in which they are related though, and that's that they're both things that fall under the justice system. I understood the person you're replying to as making a general point about their lack of faith in the justice system by juxtaposing a case with disproportionate punishment with a morally awful but unpunished case. The two examples aren't directly related, but that's why the contrast works — it's two facets of a fucked up justice system.