Ulala: the argument of "by that logic this person wouldn't have existed!" means exactly jack trash - if Person X never existed there would be Person Y who did something similiar/same -- the species doesn't revolve around single individuals - it is only influenced by their actions, and only noticably influenced by the actions of groups, typically large groups, of individuals
If they are euthanised before birth/immediately then they never have wants (a baby who is not eventually ends up having wants, needs, etc and therefore gets their human rights)
We should absolutely not let someone who is massively genetically defetive breed - except in one circumstance, they carry the non defective gene and they will do preimplantation genetic diagnosis (and seletion) for their zygotes
If someone, as an adult, wishes to die and are a patient of some sort of major illness then they should go through pysch stuff, etc to see if they're making the right decision -- if they have nothing wrong with them physically they just need psychological help, and it should be given to them.
----------------------------------------------------
Here is why I say the preventing of massively deformed (especially genetically) is a good thing -- The needs of the species vastly outweigh the need of the individual, this individual will do nothing but drain the species, this individual will never know a real life, just a pathetic dependant existance, if this individual is aborted during pregnancy excellent, if the deformation is not found until birth this individual should be humanely euthanised.
One who does not grow into a conscious thinking being doesn't really have rights, a person who will grow into a conscious thinking being has their rights because they will eventually understand them and be capable of making those decisions.