Firstly, there is no logical motive for KSing/partying with a hacker. You want to "mess" with them? Then tell me, how is Nexon supposed to differentiate between screwing with hackers and benefiting from them?
As for the whole guild issue: I think people are taking that a bit too seriously. They don't say that because there's one hacker in the guild for one day the entire guild will get banned. They're talking specifically about problem guilds, guilds that are known to hack (in my interpretation at least). For example, (G)lenshoes (I'm not sure if this is up-to-date since their leader quit recently, but it still makes my point) is a known hacker guild. Based on what Nexon has said, they would be a guild that would be banned in its entirety, no matter who was legit or not.