Didn't see the game, but from what I have read a ban is probably deserved. But I think 3 matches seems excessive, minimum is 1 game for abusing officials. This should set a precedent in relation to how the officials are treated, but it won't.
Also questions have to be raised about how late in the week they 'discovered' this offence. It has left Sydney in a horrible position.
[Edit: deleted a comment, because I found the latest copy of rules and the bit I referred too has been removed - http://www.footballaustralia.com.au/site/_content/document/00000068-source.pdf ]