First and foremost, this is not a testament against retardation of any kind, as retardation is: Normally unwanted by those not, difficult to deal with and usually looked upon with a bit of apprehension as people are not used to tolerating/dealing with it.
Normally retardation is considered a hindrance or something people (on both sides of the fence) just 'deal with.' Nobody would wish to be retarded, so to those who are... they cannot be blamed, as retardation has nothing to do with choice.
... So how does this relate to having kids?
In many ways; most of which entail the spawning of retarded ilk.
Many will agree (if not everyone), that birthing retarded offspring is extremely undesirable and is therefore one of the various and grave pitfalls of having kids. This also goes against the argument many parents will make in defense of having a retarded child, as many will claim it as an enriching endeavor. As laudable and noble as it seems, there doesn't appear to be much logic or truth to such statements.
Parents fostering a retarded child will often make statements similar to:
It's difficult to not cringe when a parent smugly proclaims that they have a feeling of completeness in their life due to their hindered child. How narrow-minded does someone need to be to require a retarded human being to validate their own existence and mitigate their insecurities?