Depends on the type of Pirates, in Impel down and the War with White Beard and the Marines showed there are all types of pirates. Pirates that do anything for money, Pirates that command honor and respect even from their enemies. Pirates that bring order to Chaos. I mean there must be a reason why those Three powers were able to keep order and balance. And I believe White Beard has already proven just how much he values his friends. Also what do you consider reliable folks, the Gorosei, that order the annihilation or Robin's homeland, Spandam and Spandime and CP9, the World's Nobles that believe they are above everyone and threat the rest as mere dirt, are those the Reliable people you speak of?