Would the violence have occurred?
I'm not condoning what happened after the game, far from it. I hate to see this happen, especially if it is involving SUFC and definitely if I end up getting caught up in it.
But,
Had the goal stood, or if the goal was correctly chalked off, would the violence have ensued? The Blades fans would've left the ground in a totally different mood and the Boro fans would've probably not been stood waiting as the handbags inside the ground before the FT whistle wouldn't have happened.
Beer and bad decisions don't go well together.
So,
If we had retrospective video evidence to check back on key decisions, this whole debacle "COULD HAVE" been avoided. i.e. if the evidence was shown on the screen and the 4th official makes the decision, all fans inside the ground would've known that there was no mistake. The Boro fans then don't goad the Blades fans, the Blades fans don't react, then the Boro fans don't have a reason to wait outside.
Same would go if the decision was proved to be correct. If the fans inside the ground can see the linesman has made the correct decision then surely it's fair do's and we move on.
I think the decision on Saturday had a lot to do with what happened afterwards.