I don't think everyone "ignores" totally, but they can discount the criticism heavily.
I agree though that with an in-person conversation, you can call someone out for their shit and they are forced to respond to you in some way, because walking away is possible but not very common if they are a friend.
It is rare that good friendships end, even in the face of very difficult conditions and words.
We need more of that online but it's hard to have, I think.
Online is a place where people live a fantasy and start to believe it is their reality.