If you are pro-choice and give people saying yes sh**t for saying yes, then you're an asshole and aren't really pro-choice. The entire freaking point of "pro-choice" is to give the pregnant woman agency over her own body. That's ok with you until a pregnant woman has a reason to do it you don't like? eat poop
This, honestly. We can talk about the moral reprehensibility of a woman choosing to terminate her pregnancy if the child would have down syndrome versus terminating any pregnancy in general, but this is what it comes down to. If you're pro-choice, or claim to be, you have to be comfortable with the notion that some women will make the difficult decision to terminate pregnancies under circumstances you don't necessarily agree with. Some people are not fit to be parents to a child with down syndrome. Sometimes the best thing to do for a child whose needs exceed what the parents are capable of giving is terminate the pregnancy. That's not to say down syndrome children aren't valid and that parents who choose to raise a down syndrome child are "abnormal", but some people are just simply not capable of it.