as a player-ref it isnt that realistic to send someone off from the other team, so the 'forced sub' is (I think) the only real option. I have done that once when a player 1st threatened me after awarding a penalty, and then later rugby tackled one of our players.
I have also seen a 'sin bin' of 2 players who got into a scuffle. strictly not within the rules but it worked a charm and both players calmed down. But it takes a confident person to make a call like that - which many players are not. everyone would rather be playing so you have to rotate including the players who arent as confident blowing the whistle or who dont know the rules that well (its not rocket science though is it).
in 95% (maybe 100%?) of close games with a player ref, the away team will go away feeling the ref screwed them, as there will generally be at least a few calls or non calls that a team feels swung the game.
I dunno, although the rules of the game themselves are simple its the implementation of the rules as a ref which I think most non-refs struggle with when forced into the role. By this I mean things like allowing advantage (how long for, how much advantage is advantage, etc) handballs (what is a natural arm position) dangerous play (how much physicality is acceptable? I think this is especially difficult when there is a big size difference between players involved). On top of this the basic stuff about positioning that refs pick up over time is missing so non-official refs often miss things because they are unsighted and this can lead to rage from players. Then there is the ever present problem of calling offsides with no linesmen...
I think confidence is the key to keep games under control but I also think a lot of people aren't confident with reffing because of the attitude players give them, so its a circular problem like the problem of no one wanting to ref in the first place. Some players also pick up on ref's lack of confidence and pressure them into making late calls and so on.
People like Coldplay and voted for the Nazis. You can't trust people.