People like Poche never bother me. There obviousness is their handicap. If I wanted to infiltrate some group I would be more like Sigismund. Not that I think Sigismund is an infiltrator. I have no idea if he is or not. Simple curiosity could explain his presence here. But I would take that approach. Be gentlemanly and courteous to everyone, while seeking to spread error at every opportunity.
A good infiltrator will be indistinguishable from a "nice guy."
"Oh Sigismund may be wrong about some things, but he's such a nice guy that we don't mind having him around."