I mean....
If I knew my sister's partner was a dangerous swindler, I'd at least confront him; "Hey, buddy, I know you tried to drug us constantly. We happen to be immune to this shit, but my sister likes you anyway. Consider the gravity of this shit and change or I'll turn around and cut your dingdong off."
By staying silent about it, they don't actually allow him some leg-room to change his behavior. He's going to continue doing what he was always doing.
If anything, Raul should feel guilty about outright torturing the husband, because of his own inaction to influence that cursed marriage.