What if Rocks was a good guy?

Why did Garp not flinch when hearing about Rocks being in God Valley if he killed an Admiral. Could it be Garp knew the guy? He definetely knew the Admiral if he is being called by Kong. Maybe Rocks was a good guy and Garp was not trying to stop him.

Maybe Rocks was also very against pirates and thats why he stabbed Loki to stop him from dreaming to becone a pirate like Garp and Luffy.