Players that act badly on the sidelines should be ejected. If a player's actions on the sidelines disrupt a game, or do something that is disrespectful to the other players, he should be ejected from the game. Yes, its a human behavior to get upset when something goes wrong. However, we must try to hold our emotions in check out in public.
If a player is ejected for their behavior on the field they should be held to the same moral code on the sidelines. Just because they aren't in the middle of the game does not give them a green light to act any way they choose. You are in charge of your emotions and people are watching you when you are in the public eye, period. Just because you simply feel like acing a fool doesn't mean you should be allowed to do it. If your on the field the message should be the same no matter where you happen to be standing. If you want to act up, take your over emotional self to the locker room and let loose.
Professional sports, by their nature, are entertainment companies. While the primary means of entertaining the audience is the sport itself, other factors including sideline outbursts can draw in more viewers resulting in more profit for the companies involved in the production. Additionally, these types of sideline antics can add intrigue to sometimes boring games, and draw greater attention to the sport in general.
If a player shows unsportsmanlike conduct toward another player, ref, or the opposing team in a serious fashion, they should be ejected. However, showing emotion on the sidelines in the presence of his own team should not be cause for ejection. It is a highly emotional sport and these players are extremely invested in their jobs.