Yes, but I was disappointed that he didn't at least change the password so that future FTP connections from the bots were refused.
It would difficult to know what to do in these situations because your choices are going to be limited to doing nothing and letting them get away with it or going vigilante and possibly exposing yourself to legal risk.
You could inform law enforcement but they are likely to either do nothing or decide to arrest you instead (I knew someone who had the police come to his house and confiscate his computer for over a year because a fellow student saw him using DOS prompt on a school computer and decided to report him for "hacking").
He had a habit of rubbing people up the wrong way, bragging about being having 'leet' computer skills (he didn't) and doing idiotic things like mass net sends at school so I'm sure it was in many ways his fault. Does show how paranoid the police can be about "hackers" though.