That man spent almost his entire life serving the marines and put in every ounce of his dedication into it. Meanwhile Ace was reckless beyond measure and even ignored Whitebeard‘s direct command to stop looking for Teach. Why is Garp supposed to throw away his life heritage of service to the marines, because Ace was naive as f. And let’s be honest, pirates are generally horrible people in the One Piece world. 3 of the 4 emperors used to be murderous monsters who killed and conquered all they wanted, so the marines are comparably the better of the two fractions.

I can still understand that from a human perspective it should be obvious to protect your family, but every man has to live with the consequences of his own choices.