The phrase "Cultural enrichment" is being used sarcastically by many people opposed to certain types of immigration.
Urban Dictionary has two entries that are sarcastic about the phrase:
Satirical term for invasion or general violence caused by pople of different culture.
Prepare for some cultural enrichment, Gondor!
Damn, this guy just got culturally enriched.
attempting to convert one's culture to your own.
you heard about Germany letting in syrian refugees? Yes lets pretend to be syrian and give them a taste of cultural enrichment!
Did any particular speech or statement give rise to "cultural enrichment" being used sarcastically so often?