I've noticed it in my friend group. My friends will freely talk about parenting and how great it is until one of the childless (by choice) friends show up. It's like we don't want them to feel bad or make it seem like we're criticizing their choice.
Also, I've definitely seen pro-parenthood posts be downvoted on Reddit. I don't mean anything obnoxious, just literally people talking about how they like parenting or how rewarding it is when it's relevant to the conversation. Obviously that's a super liberal group and that's where we see almost all of the decline, though.