I used to be laughed at a jeered at for quietly trying to do my bit towards reducing climate change and pollution in the 1980s, 1990s, early2000s. I wasn't preaching at other people or telling them they were crap for not doing the same (which was basically my mistake, I think.) then I got a told repeatedly that I didn't care about the environment because I didn't have children, that I didn't know what love was, because I didn't have children, that it didn't matter if I died or not if I don't have children, that if I do an act of kindness for someone they will be angry if they find out that I don't have children.
My caring can't have been real caring, because I don't have children.
In short, I am worthless scum, because I don't have children.
Cheer up, OP, because I am planning when best to kill myself, so that I am not breathing out carbon dioxide . I am planning to do this in a few years time (probably about two or three when I will be no longer useful to provide child care for a young relative with special needs.)
But don't worry, my mother died a few years ago so except for my husband, who is childless and a best friend and her husband, also childless, no-one will be anything other than happy that I am not around pouting the planet.
Your neighbour has been told repeatedly that he doesn't care about the planet because he doesn't have children. He has just believed it without a fight.