Correct. This is why, for example, we all agree that it is unethical to get laser eye surgery, because that would be deceiving potential mates about the genetic viability of poor vision.

As mc32 argues in a sibling comment of yours, hiding that laser surgery could be considered unethical. Situation changes when you disclose it.

Fine, require disclosure of some sort in the event of possible procreation.

That's only a partial solution, rational thought has little to do with sexual selection. I don't think we can come up with anything better though.

My partner and I got dna tests before beginning on the path of procreation. We were making a decision that affected a human being that would have no input on its coming into existence. We owe it to a child we would come to respect and love to be very conscious in every aspect of its life including its genetic viability.

Less than rational thought in such a matter, I believe is very selfish and unkind to a life that I may create.

I understand this isn't the normal way of thinking on the issue, but I wish it was more common.

The premise that backs this approach seems to be that there is a black and white “genetic standard” but the reality is surely very subtle shades of grey. What are the parameters for deciding between genetically viable and genetically unviable?

It's not a genetic standard, it's a phenotypic advantage. Taller humans are preferred by other humans and have a physical advantage over the competition so they are more likely to survive as the fittest.