"Slippery slope" and "ad hominem" are the names of fallacies. A fallacy is a defective step in logical reasoning. Hearers shouldn't be persuaded by fallacies;

"Slippery slope" and "ad hominem" are the names of fallacies. A fallacy is a defective step in logical reasoning. Hearers shouldn't be persuaded by fallacies; they're deployed in persuasive speech because (a) many people aren't familiar with logic, and find them persuasive, or (b) because the speaker isn't familiar with logic, or (c) because the speaker is out of logical arguments, but is still determined to win the argument. Or some combination of the three.