Fridge Logic: Pirates aren't nice people, they're thieves. Captain Feathersword the Friendly Pirate is a pirate. It's equal to having a character today called "General Ticklebomb the Friendly Terrorist".
Captain Feathersword, as implied by his moniker, has a feather for a sword. He has to be friendly...as would a terrorist whose bombs induced tickles instead of death.
Guess we've got our new culturally relevant children's show character!