Why do you say that? They could very well be good friends.
And he may be evil but it’s because he believes in the law very strongly
believing in the law very strongly doesn't take away from his evil even one bit , Fujitora and GB cannot possibly be friends , compare this :
- First thing Aramaki does in Wano is get ready to slaughter the civilians
- First thing Fujitora does in Dressrosa is get ready to protect all the civilians
It's pretty obvious , they have polar opposite interpretation of "justice" just like Akainu and Aokiji