-cide is a latin suffix that quite simply means "kill". Trying to call ethnic cleansing genocide is like calling divorce mariticide or moving away from home patricide.
The correct latin term would be something like "expulsio gentium".
Raphael Lemkin, the guy who first coined the term "genocide", considered "cultural genocide" (the killing of a culture if you will), a central component of genocide.
Also, I don't know if you've noticed, but people generally resist being ethnic cleansed, and so the perpetrators have to kill a lot of them.
The correct latin term would be something like "expulsio gentium".