They just hate pirates for the mere fact they are pirates
Look at Koby and Luffy
Koby admires Luffy, Luffy saved his life after all in fact Koby is always glazing Luffy, but last chapter now Koby wants to oppose Luffy's dream?
If he's such a good guy who you look up to, why do you want to arrest him?
Why is being pirate king even illegal from what we know it seems being Pirate King means you save the world in the process
Another character that's weird is Garp, his sons are pirates and he knows they are good people but yet he sits by Ace and let's the marines try to execute him despite knowing Ace isn't a criminal nor a bad guy, he is just a pirate.
Sometimes the marines will accept this like Fujitora, he notices Luffy is a good guy who saves a village so he let's him escape while posturing like he's going to arrest him
All in all, the marines don't really have a good reason to oppose pirates especially when they let the celestial dragons commit crimes against innocent people, they are an organization in one piece that doesn't make any sense
Look at Koby and Luffy
Koby admires Luffy, Luffy saved his life after all in fact Koby is always glazing Luffy, but last chapter now Koby wants to oppose Luffy's dream?
If he's such a good guy who you look up to, why do you want to arrest him?
Why is being pirate king even illegal from what we know it seems being Pirate King means you save the world in the process
Another character that's weird is Garp, his sons are pirates and he knows they are good people but yet he sits by Ace and let's the marines try to execute him despite knowing Ace isn't a criminal nor a bad guy, he is just a pirate.
Sometimes the marines will accept this like Fujitora, he notices Luffy is a good guy who saves a village so he let's him escape while posturing like he's going to arrest him
All in all, the marines don't really have a good reason to oppose pirates especially when they let the celestial dragons commit crimes against innocent people, they are an organization in one piece that doesn't make any sense