I absolutely agree people need to vent etc, but I am bewildered because I genuinely don't really see arrogant people thinking their advice ought to be followed??

I don't really get it?

As far as I see it - advice or opinions are given, and it is up to the thread-starter to choose if they want to engage with it, retort to it saying no actually you are missing the point, read it and consider it for later, or just read and feel less alone because somebody has gone through something similar.

A thread-starter can't control responses from every individual. This is the internet, it's a forum, if you post there is a risk you will hear stuff that does not expressly suit you.