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You have completely missed the moral issue, which is entangled with the logical one Chomsky evidently evinsced. People are going to have sex. Condoms fail, as do diaphrams and spermicides. Even the pill is not full-proof. And many, many people who have sex will wind up with an unwanted pregnancy or, worse still, an unsupportable pregnancy, whether due to health or economic issues.
According to your moral - or perhaps more accurately - ethical argument such people should be condemned (and that is the proper term) to an 18 year burden they did not want or, again worse still, cannot bear. And what of those people who cannot bear that burden? What you have failed to consider is the hellish life the unaborted child in question will have to endure. And for what? To prove that "personal responsibility" is an absolute value foresaking all others? That, sir, is what is commonly known as a "fallacy."