1. Yes, children need self-care. But so do adults. Just as it is wrong to tell someone they can't take care of their child, I'd say it's equally wrong to tell an adult that they can't, for example, get their exercise time, because I would consider that also a human necessity. You risk early death if you do not exercise. For medical reasons I don't need to state here, the risk may be even higher for me personally if I don't get that time. Other adults have other medical conditions they need to attend to. However, not all workplaces recognize these as on par with taking care of children.
2. Those that choose not to have children may also be playing essential roles in our society in their off-hours. Heck, they may be volunteering at the Red Cross and saving other children from death, who knows, that may be why they chose not to have kids. Should we judge?
3. Let's not underestimate how important mental health is to society. People will die (from various causes, including suicide) if they are made to work late every day. Yes, I agree that children need to be taken care of. But the response to that shouldn't be to take an unreasonable work share given to a working parent and shove the excess onto the single/child-less workers in the same organization to slave away for 80 hours a week. This actually happens, and I have seen it happen. Instead, the response should be to give everyone a fair, normal 40-hour work share and let them do whatever they need or want to with their spare time.