Hoowa! ...as Pacino would say
Selfish--I usually get it from the religious, saying that I'm being selfish by not carrying on the family name(...I'm female so...wtf) or denying my "sole purpose in life" and I think a lot of them are like Mormons--they think somehow god had plans for souls or whatever, and I'm "denying' some range of future broods by choosing the SMART choice which is to not have children because I can't afford them.
It's not selfish--it's smart to choose to be childfree when you know a child would be unloved and possibly resented.
I don't see how it's selfish to elect not to give yourself additional, unnecessary responsibilities. It would be selfish to take on the responsibility (have a baby) and then neglect it--and unwilling parents don't make good parents.
Your defining of "selfish" is more appropriate for breeders than non-breeders. It's selfish to make as many babies as you want that take up more resources and more land from other species. It's selfish to have no limit to your own species' population while practicing "population control" on other species that aren't even overpopulated, just shoved into smaller spaces to accommodate you.
And about those people who go through fertility treatments instead of adopting because "I want my own baby"...unbelievably selfish. It's selfish to pressure your wife or your daughter to go through a pregnancy she doesn't want just so you can see another little version of you running around (which is by itself pretty selfish).
Often when someone calls someone else "selfish" it is because that person isn't giving them what THEY themselves want. In other words, they have their own selfishness.
I think about the toddler who was run over by two vans, while pedestrians, bike riders, and drivers glanced at her bloody injuries and went on by. How many of those nightmarish, callous people, have a child themselves? Most? All? Many of the Chinese, themselves, are suggesting that overpopulation led to this indifference to the little girl. Of course traditional sexism, and a history of infanticide of female babies must be taken into account. Still, if there were far fewer people, and not everyone was expected to reproduce, I think each child would be considered special. The childfree could be like aunties and uncles to the children. I hate that children are considered the property of their parents.
Anyone who dared to call me selfish for having no children will surely get an earful from me, and maybe a kick in the ankle. There is nothing wrong with me - I've been FIXED!