It seems the common denominator os Sheister. Simple fact is, you took him into your kingdom knowing exactly how he'd been playing and what he'd been up to, and now you're acting all high and mighty that someone has come after him once he's in your esteemed kingdom.
You don't get to take the moral highground when you invite a known troublemaker into your kingdom, and he doesn't get to wipe the slate clean by getting the right invite
Maybe you should consider the company you keep and the reputation they gain you a little more.