Why do we live in a world where people deem themselves to be so self-righteous that they can publicly insult another human being? Am I perfect? No. Have I had my outbursts in the car at other distracted drivers? Yes. But I would never approach a complete stranger, in person or online, and give them my mean-girl, unsolicited opinion.
It's all a matter of perception and communication. When children are home they often see mothers preparing meals, helping with homework, folding laundry and doing other tasks that seem familiar, easy and routine. They're not as aware of what else mothers out of the full-time workforce do while children are at school.