1. Start with a common assumption, vaguely and generally accepted by most, but actually, in detail, false.
(Monkeys are just like mankind)
2. Accelerate to an absurd deduction based on the above assumption that will fascinate many.
(Mankind therefore came from monkeys)
3. Present the view as fact that, if not wholly accepted, only proves the listener's ignorance and low mental capacity.
(Evolution is an established fact that only the ignorant refuse to accept.)
4. Develop a following and give it a look of prestige so that borderliners will want to be in, regardless of any logic or moral issues.
(Scientists accept evolution. Why don't you?)