Jinbo fucked up releasing Arlong into the wild.
He put a bullet into Bellemere's skull, enslaved an entire town for over a decade.
Sanji was completely justified here, considering how much Nami means to him.
Remember that he immediately kicked the shit out of Franky as soon as he learned his name on the Sea Train, due to what Franky and his family did to Usopp.
Sanji takes care of his nakamas.