Because it can be abused and turned against people in malicious ways. On top of the fact that it invades your privacy.
As one quoted in the article, "In the real world, I don't demand to see an ID as a precautionary measure".
The whole notion about having so called consequences for what people say on the internet often comes from vindictive, bad people who want to hurt others because they don't agree with them. That's not the kind of people you should make laws in favor of.