Problems are, Kaku, Lucci, and all CP9 were raised up since infant/since they not even aware of themselves, indoctrinated with the clumsy ideas of right and wrong.
If observed carefully, Kaku did not directly do anything to his own ally or anyone at W7. He only get his hand down to the pirates, cause in his logic at first, all pirates are evil. Only through this event he could refresh his mind on the matters.
Lucci, on the other hand, bashed Iceberg/Paulie and the new CP9, but it was with his own reason. But he didn't do anything bad to Chimney/Gonbe.
He told us that as a carnivore Zoon, he can control the strength to the maximum limit. But there was his soft side.
No matter how ferocious it was, an animal still have brain and feeling.
I never interact with leopards, but I had some experience with tigers.
A tiger is a caring loving animal, I can guarantee.
Lucci could say that he is bloodlust or etc, but actually he thinks a lot about the situation, plays carefully in the edge of legal ways, and acknowledging Luffy's good leadership.
I don't think he really wanted to get rid of the mugiwaras, cause if he did, he could abandon any of Spandam's command and destroy them all in the first place.
Then, it was the WG behind all of them.
We can judge that while most of the soldiers are purely joining to stand for justice, it was natural that some are trying to get their own profit…
but the SYSTEM itself are corrupted.
There was the dark justice CP9.
A court that never vote not guilty.
And... the keeping of criminals, Shichibukai.
As for the system had stand through 800 years, it was good enough to maintain STATUS QUO. It was fine with the central kingdoms that could manage their own country, but it was not with the remote village on a faraway islands. There are some limit of basic human/creature rights.
And that's the duty of Dragon as revolutionist, and the pirates as a bunch of people with free lifestyle.