Butler left the field immediately after the incident before being taken to hospital where he had to recieve stitches to his lip.
United's youth team coach Paul Wilson said: "It was an absolutely disgraceful incident, everybody at out club and their club was just gobsmacked (Excuse the pun). There was nothing in the game and that just came out of the blue."
It was the first time the Iron have sent a team to Barton Town and unfortunately for the Central Midlands League side, United's assistant manager Russ Wilcox made it clear it would be the last.
He said: "It was a nasty cut and an incident you don't need. You try to do these non-league side's a favour and for me that is another one off the list. We will not be taking a side there again".
Brown scored four times for United, with Andy Parton finding the net twice to progress to the final where they will play Winterton Town or Appleby Frodingham.