they're not real so their actions cannot be considered just or unjust, at least in a practical sense. a better question would be:
why did my wife leave me?
I always think that forcefully changing someone's heart is not a just action.
If any of the phantom thieves wish to talk about this matter further i'm always willing to listen (wink wonk)
Archer you're under arrest Somehow, Akechi reminds me of myself - aside from the fact that I do things myself, not stage them. And of course they're just, with Achilles by my side - It is my job to ensure that criminals are tried for crimes