While this might seem like a bunch of edl scum bags behaving like loonies, the reality of the situation is much more serious than that.
MP Joe Cox was murdered by a right wing terrorist who shot and stabbed her repeatedly in the street while shouting "Britain first."
https://en.m.wikipedia.org/wiki/Murder_of_Jo_Cox
The message of violence was made very clear when a gallows with a noose was wheeled outside of where Khan was speaking. It was a message that Khan should be hung in the street and killed just like Joe Cox. And it also sends a message to those who dare speak up or stand in the way of the right wing racist agenda and that message is one of death.
These people aren't just skin head morons with too much time on their hands. This was a tactical monauver of getting the message out there. They want that message to reach a person who is willing to follow through with the same violence that took the life of Joe Cox.