Ohhhh. I think I get it now.
The reason he won't condemn the hero for being a cheating bastard is because the author also intends for Silva to get a harem. I felt like that was weirdly glossed over.
Anyway, clearly the other reincarnator let being the hero get to his head. Doing this sort of thing might be fine when it's just a game, but if you do it to real people, you're just a psychopath.
I guess the scenario was always broken, from that point of view. In fact, could it be this other reincarnator's utter lack of charisma and care that drove Charlie into Silva's arms in the first place?
If you find yourself dealing with a capable comrade with a shitty personality and you encounter an even more capable fighter with a good personality, it only makes sense to be interested in the new guy.