Actually Elrond says at the council that both he and Cirdan tried to talk Isildur out of keeping the Ring but he refused to listen. However in fairness to Isildur he doesn't seem to have intended to use it, just keep it as a trophy and heirloom - impossible of course but he fooled himself into believing that it was.
As for Bilbo - well the ethics of the situation are a bit cloudy but there's no question Gollum's intentions were murderous, and Bilbo took the only possible course to get himself out of the caverns alive.
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