People with currently-known genes for conditions like Tay-Sachs (recessive gene, if a baby gets two copies they are a normal baby the first several months, then get progressive nerve damage until they die around three), or Huntington's (relevant gene is dominant, but condition manifests in adulthood) may choose not to have kids, or use technology like PGD to select embryos without the relevant genes, or in the case of recessive genes may refuse as spouse any potential partner that also has the gene.

Those are complicated decisions, and nothing should be forced, but it's important to be able to talk about. There shouldn't be a taboo on talking about how parents' decisions affect their children, even if those decisions involve genetics.

When I was still on reddit, I would occasionally come across a comment I liked.

It could be something as simple as "The (local sports team) is going to (do something sports related) this year!"

And I, without context, would reply "Please have babies."

Sometimes massive upvotes. Sometimes massive downvotes.

NEVER made any sense. And thats fine.

Why allow child to be born with sickle cell anemia if they are going live a lifetime of pain?

It is perfectly understandable that eugenics has a bad name because it has been abused. Although, you should read up more on the topic as it is actually more nuanced.