This tactic exploits the widespread irrational tendence of the human mind to reason on the basis of words/denominations rather than on concepts/definitions.
In case some progressive (i.e.: liberatory, empowering) ideal becomes too widespread to be directly countered, if that ideal can be identified by a name (or even a symbol), then it can be "polluted" by introducing extraneous concepts into its definition (or by expunging integral parts of it), and this can go as far as to entirely invert the original meaning; since most people do not reason on concepts but only on their name/symbols, they most likely won't notice the trick, and will unconsciously accept the new meaning in order not to "betray" it. In this way is it possible for propagandists to push regressive agendas by hiding them inside widely upheld progressive names/symbols. The trick is to never definitely remove the original meaning, but to always keep a subtle level of ambiguity between the two opposite meanings; this ensures the tactic will never exhaust its manipulatory power (for example, by letting all people eventually re-adjust their thoughts to the new definition) and will always be useful to manipulate people in multiple ways at once: people who are first exposed to the "old" (progressive) definition will embrace the name/symbol and by doing so, they will unconsciously be manipulated into embracing and promoting its new opposite (regressive) meaning; specularly, people exposed to the "new" (regressive) definition will reject it, and by doing so, will also reject the progressive ideals it originally represented, with the additional result of promoting division and infighting between the two groups even though their actual ideals are very similar. The same tactic can be used in the opposite way, that is: to introduce progressive meanings into widely rebuked names/symbols, in order to either prevent people from supporting them, or forcing them to support both at the same time; the ultimate result is exactly the same as the one described above. The combined use of these tactics can result in a complete inversion of the entire political/philosophical/scientific terminology: nearly every single word has been twisted beyond recognition, and is usually used with the diametral opposite meaning to its original one, first by the mass-media and, consequently, by the rest of the people, with obvious disastrous consequences for any kind of rational debate towards any kind of truth or social progress.