WATER MARGIN is ridiculous. I’m really not sure what to make of these characters

I really can’t tell whether this book is serious or joking when it talks about the virtue and heroism of its bandit-protagonists. I think it’s a little of both. I know that morals were different in the 15th century, when this was written, but some of these behaviors are so appalling that there is no way the author could have approved. 

For instance, after winning a battle the bandits sit down with the captured general of the opposing side, and they just sort of chill and ask him to join their side. And he’s like no I’m loyal to the emperor. And anyway my family is in town and they’d be killed if I betrayed my post. 

So the bandits detain the general for a night and then secretly take his armor and put it on one of their number and then they go on a raid against the nearby town. So when the general gets home, he finds that everybody thinks he has defected and that the local magistrate has already executed his family!

And then the general goes back to the bandits and they’re like, umm, we did that in order to force you to join us. And then he does!!!

I mean I know all is fair in love and war, but this seems excessive. It was a targeted act against a single man, conducted with the sole intention of ruining his reputation and getting rid of his family.