Is the mafia corrupt?
You might wish it served to protect your property, widows, and orphans-- after all, that's what the mafia would claim it does-- but in reality, it steals your money, threatens you with violence, violates your rights, and murders people.
Corruption is something like rust, which isn't necessary, but damages and weakens the structure. Corruption isn't just that the true shape of the thing isn't to your liking. Rust on your blade is corruption; the sharp edge isn't.
You might believe the bad things the mafia does are signs of corruption, but those are really the things that make it the mafia rather than a social club. Without those unethical acts, it wouldn't be the mafia. You can't get rid of the things you might inaccurately call "corruption" without abolishing the mafia entirely.
Oh, wait, did I say "mafia"? I meant "government".