A shrinking deaf community has nothing at all to do with ethnic cleansing, and social support does not shrink for less common diseases - it's usually the opposite, with support proportional to how rare and inconvenient the disability is.

Let's try a small thought experiment: Some birth defects stem from dietary issues in the mother during pregnancy, like folic acid deficiency or alcohol consumption.

Let's imagine that we discover that deaf children are primarily caused by a particular vitamin deficiency during pregnancy. We can then either spread the information so parents can supplement, or even fortify foods and cause the community to massively decline or even disappear - or we could withold the information on the vitamins to artificially maintain the population of the deaf community.

You could even extend it to a scenario where we end up relying more and more on artificial insemination or other early processing - the impact of many dietary deficiencies happen extremely early, so to maintain the community we would then have to artificially cause said deficiency to maintain the population of the deaf community.

Heck, we can always just make people deaf later if you wanted to maintain their community. We could also make more people get into "accidents" so that the quadriplegic community is maintained. Sounds absolutely insane when you start to discuss maintaining the population of disabled communities, doesn't it?

Back to the topic, cleansing of the deaf in this context implies a hatred for deaf people in general and wanting to remove all deaf people, which is an emotion entirely unrelated to sympethesizing with the disability of being deaf and wanting to avoid causing more such disability.