Some parents, many actually, are truly awful people and put their children through hell and leave them with lasting psychological issues. There's no excuse. Though I understand that there are many things parents do that non-parents judge them for just because they don't understand how difficult and taxing children can be, things that they'd probably do themselves eventually if they had children. It's not ideal but I guess it's understandable.
I don't give advice because I'm too shy and also I know that parents hate getting advice on parenting from non-parents. Even if I think the children are unnecessarily suffering and/or are being conditioned in the worst way, I don't give advice. I'm not sure if that's the best thing to do or if I'm just a coward.
Also all parents deserve judgment for bringing more people into this God-forsaken world of suffering. But I usually don't think about that just because someone has kids, it takes special circumstances for that to annoy me.