How it's apparently OK for people who have children to treat people who don't like they're children themselves. That, and the implication that the people without kids should always be willing to jump to help out the people who do. I had this basic conversation with three different co-workers:
"I noticed that (manager) let you have a week off at the end of the month, how did you get away with that? We've already got a bunch of people scheduled off that put in way ahead of you. It's going to be a nightmare for everyone still here."
"I got a jury duty notice for April 30, I don't know how many days they're going to need me but I'm obviously going to need those days off. The week is tentative, sometimes it takes that long."
"But you get off at 6:30 in the morning! (I work nights) You can easily make it down there in time."
"So, you want me to work basically 16-hour shifts with two commutes, thus guaranteeing I get 4, 5 hours of sleep maximum in addition to not being able to do anything else."
"Oh, don't be such a baby. When you have kids, 16 hours of work on 4-5 hours sleep is something you deal with every day. You should learn to deal with it now."