That is utterly, irredeemably mortifying.
So if a player headbutts another player who squares up to him it's fine because it's only self defence? Or if the referee starts handing out knuckledusters everytime he gets absolutely surrounded by baying players who are screaming in his face (which we as a club never do, btw), all good? fecking nonsense.
Robbo walks over to him and maybe brushes against his arm so he's justified in throwing an elbow? You'd get done for assault in the real world.
If the linesmen is scared by that he probably shouldn't leave his house, lest he be elbowing anyone who looks at him funny on the street out of fear for his safety.