Why do worms?
Trauma responses are very low-level, far below the threshold of consciousness or meaningful brain function of any type. It is why they anaesthetize even the most primitive of creatures when doing research -- to minimize a trauma response that will interfere with the research being performed. Since they are simply killing the fetus, mitigating the trauma response is apparently not a significant concern for the abortionists.
A response to physical trauma is orthogonal to consciousness or even having a real CNS to speak of, and conflating one with the other is damaging to the credibility of the arguments against abortion.
Wrong. As far as I know, we are the only species that teaches our children not to cause needless pain, no matter how it's measured. We wouldn't encourage children to torture even worms.
Part of the reasoning against abortion is the harm it does to the mother, the doctor, and society that allows the redefinition of humans as less than human-enough.