Reasonable people can debate when the latest legal abortion should be. The parent comment simply referred to abortion. Generally those opposed to abortion believe that abortion should be illegal from egg fertilization, or even prior to this by restricting birth control.

I might tend to agree with you that 24 weeks is too late based on a quick look around:

"By 22 weeks, your baby's nervous system completely 'connects'. The vital link between their brain and spinal cord (the brain stem) now matures and many nerve cells make vigorous connections. When this happens your baby becomes capable of recognising warmth, light, sound and pain. While primitive brain waves have been detected in unborn babies as early as 7 weeks, it is not until 22 weeks that sustained patterns can definitely be recorded. Some women will now notice that their baby 'jumps' with a loud sound. "

http://www.birth.com.au/Pregnancy-week-by-week/Weeks-21-22

If no brainwaves have been detected prior to 7 weeks, I'd probably set that as the lower bound for when abortion should be legal.