So basically you want someone to be fair with pirates who steal, kill and rape people ?
For Aka Inu, all pirates are the same. Only wbp and SHP are good people. Roger and RHP maybe also. But 99,99% others are dangerous.
Aka Inu did the right thing, no need to be kind with criminals ...
This.
Sakazuki is a Marine Admiral. It's weird how people think he should treat Pirates with respect. Pirates deserves no respect at all, they are serious criminals who more often than not murder a lot of people (this being a kids show and all, they are not really rapy, but they sure as hell kill a lot of people).
Sakazuki sure has honor, loved ones, family, friends. But he also has a job. He must protect and enforce the law. He saw a chance to kill a Yonko and he took it.
The son of Roger and Dragon were also 550M and 300M Pirates with Dead or Alive bounties on their head. He killed Ace and if the plot armor were the least bit thinner Luffy would be dead too.
It's not a matter of honor, it's the law and it's his job, simple as that. Pirates have Dead or Alive bounties on their head for a reason: the law state that if you choose to lead a life of crime, you are forfeiting said life, in the sense that a bounty will be put on your head, you can legally by killed and have money collected on your dead corpse.
Being a pirate is bad for your health, don't it if you don't wanna be chased and killed.
Also, it is a Marine's duty to enforce said law. You are paid, trained and the job you are expected to do, among many other dutes, is to hunt and kill fucking pirates.
Sakazuki attacking Coby is up for debate. The way he handled pirates no, nothing wrong with that, burn them all.