To neutralize something is to render it harmless by enacting a countering or opposing effect. That is why it is called carbon <em>neutrality </em>in the first place. To offset something is, by definition, the exact same thing, therefore making <em>neutralize</em> the best synonym to the word offset.
probably because he knew the odds of them surviving were pretty low and after what he had been through i suppose he wouldn't want them to end up like him.