Its part of the game at that level, people pay their money and voice their opinion. I am a fan of football as well as a ref, and sometimes things get to you. I have seen at matches when AR have got a number of key decisions wrong. Fans will get upset and shout things, but lets be honest 99% of the time its just that, just shouting things and they go away and have a little moan but thats the end of it.
At grassroots a little different as most of the time you are on your own and a lot of the assaults etc happen at that level so things need to be put in place. Although I am a Port Vale fan and we sadly had some idiot chase the ref (although on that day, the ref in question had a shocker, not saying he was right in anyway to chase the ref, but I understand the reason.)