Ok....in the comics Venom hates spider-man because spider-man is the one who got him fired and all that...movie Venom hates Peter Parker, Peter is the one who proved Eddies picture was a fake and also in Eddies eyes stole Gwen from him...now in the movie had Eddie never found out Pete was spider-man then he may never have found out and instead wouldn't go after spider-man but he would go after Peter not knowing he is spider-man but the symbiote woulda told him probably. In the comics Eddie hates spider-man and woulda gone after spider-man rather than Pete but the symbiote knew Pete was spider-man and so therefore Eddie knew Pete was spider-man.