It's about setting an example, What suarez did has been seen by many kids around the world, therefore it's only natural to give him a good lesson. It's not the first time that he's shown this kind of behavior (racial slur on Evra, biting another player) so why should they be nice to people like him.
I'd rather see someone kicking or pushing than biting. Biting is for animals... And Suarez doesn't seem to learn from his actions, he apologized yes but he's probably going to do some stupid stuff soon so hopefully he'll learn that he won't get away with it anymore.
Oh and i should add that he didn't just bite Ivanovic, he lied in front of the referee's face and acted like it was Ivanovic who hurt him instead... Suarez was faking an injury on his leg and the referee blamed Ivanovic instead, like seriously he deserve this ban.
The craziest thing is that people feel that he's been nice enough to apologize. But they don't get that he didn't specifically want to apologize, he had NO choice because you always need to apologize for this kind of stuff or the consequences are going to be much bigger.
A 3 game ban would have been sufficient for a player with no past like him.