Well - you basically made the exact reply he was expecting.

I think that letting serial killers out of jail is a bad idea, yes. The reason why we should keep serial killers in jail, though, is not that they're serial killers - it's that, in most cases, they tend to not care and will willingly kill again.

If there is a serial killer who is provably not sociopathic and who can actually become reformed, then that person should be eventually let out of jail. That is a very difficult standard to meet.