The key word being absurd. Your previous projection of your argument that: "If the fact that abortion kills potential rapists, murderers, molesters, etc., is a justification for abortion, then you have to admit that if we killed all the kindergarteners in America, that would be justified, too, because if we did, we would also be killing lots of potential rapists, murderers, molesters, etc."
Equating the two is absurd.
What is being equated is not the SUBJECTS (babies in the womb/children in kindergarten) of the two arguments, but the FORM of the two arguments, which shows that BOTH arguments are absurd.
Objecting to "equating the two [subjects]" is fundamentally the same as objecting to "changing the subject." Making that objection is a confession that one has failed to understand the formal, logical point being made, having been distracted by the subjects of the two arguments.
I am sure there is a good Wikipedia article on reductio ad absurdum. (Since it isn't a political matter that the masters of Wikipedia would interfere with.)
No, equating the two is purely logical; equal action, equal outcome.