I would hazard a guess that some HCPs feel strongly about making sure the option of termination is entertained because they will be the ones picking up the pieces if they parents decide that they can't cope.
I have worked with HCAs who have cared for people with learning disability who have gone out into the community and been gang raped or used as slaves for running drugs and ended up in prison. HCPs who work in the area of serious LD are the first to say that the myths of cute Down's babies hide the serious and devastating consequences of having a LD without adequate support. These children grow from vulnerable babies into vulnerable adults.
Whilst diversity is a positive thing, I would never knowingly choose to bring a child into the world who is more likely to be emotionally, physically, financially, emotionally and sexually abused than a child without their condition. I would not make my child into a political statement when the risk is that they will be horrifically manipulated or neglected by society. It is just not fair.
People with Down's are visibly so, and certain people will always seek out and target them since care in the community has taken over and they cannot be kept safe.