I had someone say the same thing to me when I was a the mall about two weeks ago. I was in the food court with Leah and the women next to me was watching the kids in the playground there and she said to me "While I don't support your choice to have a child it is great to see you've chosen to only add one more mouth to feed to this planet." O_O I was sitting so I guess she didn't see the clearly pregnant belly. I was intrigued and asked that she explain herself further...so she went on about overpopulation (not a theory I actually support. We have plenty of resources in the world they just aren't distributed fairly throughout...and there are plenty of people choosing not to have big families that if someone does have a big family it all kind of evens out anyway) and she went on about all the unadopted international children (completely ignoring the millions of them right here in the US).
Childfree
That type of thinking is flawed I think.