Remember that "fallacy" means "argument form not guaranteed to produce true results given true inputs."
Outside the context of rigorous mathematical proofs, many fallacies are legitimate, helpful tools.
See for instance "post hoc ergo propter hoc": https://xkcd.com/552/
Or the slippery slope fallacy, as it is known in less ideological circles. The "paradox" simply asserts that a tolerant society will be usurped by intolerant actors. It is in all respects a slippery slope argument.