All very odd. Players expect tackles, so the authorities judge a red card for a bad one to be worth three games off. Jumping into the crowd and kicking a spectator is not contemplated by anybody, so is worth 9 months off. Biting an opponent, quite deliberately, with premeditation, is somewhere between the two and worth longer than racially abusing an opponent (Suarez got 8 games off for that before) so is ten games.
Time for some 'sentencing guidelines' like courts have ! As mentioned, rugby takes a tougher line on biting; 18 months or more off. Why soccer is so feeble must be a question of money, or something equally irrelevant. If Suarez got banned for a season he really ought not to be able to complain, but other clubs with players of value and like him might think that a dangerous precedent.