Lucifer's Hammer/YMMV

Harsher in Hindsight: at the very end; the heroes successfully defend the last operational nuclear power plant in the world from the cannibal environmentalist fundies(at the cost of their Gadgeteer Genius - he was diabetic, but chose to make mustard gas to kill the cannibals instead of insulin), but say that to rebuild civilization, they have to hunt down the fundies and either take all their weapons or kill them all because it would only take one lucky mortar shot to destroy the plant. To save civilization, they have to fight The War on Terror, and be willing to commit genocide if their enemies refuse to surrender.
Unfortunate Implications: To quote RationalWiki, this is a novel where "a group led by a former U.S. senator who set up a particularly hardline form of government are the good guys, trying to keep at bay the roaming bands of hippies, black nationalists and cannibals." Another page on the same wiki criticises the book as viciously misogynistic, mentioning a gleeful passage about "the death of feminism".

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