[Folwren]

Thank you Kuruharan. Right in the quote you quoted, Mansun, Gandalf said he deserved it.

Just because someone can not see into the future does not mean that they can not deal out punishment. There are crimes that deserve death, and even mortals and those that are immortal and wise are allowed and possibly expected to kill them for it.

Consider it thusly - If Bilbo had killed Gollum when he had a chance, Gandalf wouldn't have rebuked him, would he? Probably said something along the lines, "Well, well, well, I think there's more to this hobbit than meets the eye at first."

Or, if Gandalf himself had come across Gollum cradle stealing, I somehow think he wouldn't've spared his life.

Gandalf's rebuke to Frodo was not a question of 'If Gollum were brought to court for his crimes he wouldn't be killed' it was 'That's not very nice of you, Frodo, nor very wise. The fact that Bilbo didn't kill him when he had the chance should tell you that Gollum's time hadn't yet come. Don't be so hasty in such a matter and think before you speak and act.'