@SuburbanVagabond Pretend to share their views 100% at first (while being careful not to let their propaganda or even your own words affect your real views, mind you), gain their trust over time as you become a fairly well-known regular in their community, then (after a long enough period... I'd say at least weeks, better months) the payload: start subtly & carefully exploiting the logical inconsistencies in their ideology to seed doubt, discord, & sectarian division w/o raising too much alarm.