We're just getting into a pointless gray area when that argument is made. Doesn't having work hours that don't match with school hours discriminate against parents? Isn't a position with on-call responsibilities inherently discriminating against people with more familial commitments?

I don't think it's the employer's responsibility to tailor the job to match a candidate's chosen lifestyle, or that not doing so means you're discriminating. I think people need to be responsible for their own decisions, and if that means you're less competitive relative to another candidate, that is not the employer or the other candidate's fault.