Being different is tough. But I guess some kinds of differences are more "tolerated" than others.
I just like to think that when others are really nasty and mean, it's mostly jealousy. We're an "eye-sore" to them because we didn't give in to pressure, but they did. If they're really just purely happy about having kids of their own, they don't have to judge others for not having any, but I'd think it's because sometimes they regret it, or just feel that it's too tough, that when we say we choose to be free from all that, they need to "attack" in some way, or else they might break down and cry ...
in a way, they're really sad. (*sigh*)