Pepe and Costa did a headbutt in two WC matches with similarly high viewer count. Nothing happened to Costa and Pepe got a small punishment.
Do you consider Pepe on Muller a headbutt ? really Hammy.. it was a touch .... and he was red carded for it.. Suarez not only escaped punishment he pretended he was hurt
compare to Zidane punishment in the final of 2006 , Red card & 3 match suspension & 3 days of community service
Tassoti Elbow to Lucho was an 8 match ban , Leonardo to Tab Ramos 4 match ban (if I remember correctly ) yet Suarez just last year was handed a 10 match ban for similar act and FIFA said wide & clear that Suarez punishment will not be separate from his history as an offender of the same act... there is no rules in football regarding biting however if Suarez was an HIV positive player he is causing fatality to other players with his bites
the English FA handed Saurez a 10 match ban last season & a year later in the World cup he pull the same shit.. it's normal you INCREASE the punishment ..maybe he will seek treatment