I don't think anyone is writing anyone off, or wishing you didn't exist etc. I do understand why it could feel like that, but I think we all need to be aware that autism, either living with it or living with someone with it, or both is hard going at times. And at times, parents of autistic children are on their knees.
This thread was started by someone who wanted to reach out. Who needed to get her feelings out, and probably get some empathy and understanding. Perhaps she turned to MN to avoid an outburst at home? I know I had my own meltdown at the weekend, I hyperventilate and sob.

Op isn't wanting any one you with autism to disappear, to not have been born. Right now, she just wants it out of her life for a bit. I get that. I REALLY get that!
By admitting that, she isn't saying she hates anyone, or her son, or wants anything bad to happen to anyone. By agreeing with her, empathizing with her, going a bit further (in the case of one pp) saying that she wished they could screen for it, no one is doing or meaning anyone here any harm or malice.
Please allow our place to vent without telling us what you think we are doing, or what you think we are thinking. Please do not see what isn't there in our words or actions. And of course, you deserve the same respect too.