It's partly that Marxy idea that the ideas of the age are the ideas of the ruling class. People think if they spout liberal talking points that makes them a good person.

To be a good person you have to make self-sacrifices, e.g. getting up early to do things for your family when you don't feel like it.

People try to be moral by spouting ideas.

And it's often done in a competitive way, by means of a put-down.

People will talk about how pædophiles are bad, terrible people. Well of course they fucking are, we all know that. Just because you said, "I think pædophiles are bad!" doesn't make you good. It's not a brave thing to say. You're just trying to show others that you're on the right side of morality so they'll give you a free pass.

Why do you feel the need to say "I think serial killers are bad, anyone agree??" Probably because you know you're a shit person and you have to prove to society that you're less shit than someone; you are good by comparison.