Yeah, I hear ya...and, for the more 'extreme' beliefs (especially those that would maybe set them up for more interpersonal conflict/aggression), I'd just fall back on some of the CBT literature for how to deal with delusions / psychosis / personality disorders. I think that a non-judgmental, curious, Socratic approach is best. And try to preferentially focus more on what the IMPACT (interpersonally, intra-personally (e.g., symptoms/suffering), practically (do they lose jobs because of their beliefs?)) of having the beliefs is upon their life and functioning (and their life goals) rather than trying to debate or rationally refute the specific beliefs--I tend to get more therapeutic mileage out of such an approach. Also, it could be a real window into their value systems (and network of beliefs) if you could take a deep dive into why such beliefs are so important to them...for example, do they value individual liberty, autonomy, truth, hard work, transparency, whatever? And then, again, use a Socratic approach to help them realistically assess how their cognitive/affective/behavioral patterns (which may be fuelled by their 'conspiracy' beliefs) are actually impacting their valued outcomes and life goals. For example, are they alienating their wives/friends/family through engaging in conversations about these beliefs trying to convince them? What motivates them to do so? Okay, so now we identify a value that you want to look out for the safety of your family because it is important to you. Is there an alternative, socially-skilled, and more tolerable (to the family member) way of trying to better look out for their safety that they would agree is a good idea? (e.g., installing a home security system, if they agree that it's a good idea). The client could identify 'safety to family because I love them' as an important value or life goal and be asked if his current preoccupation with whatever 'theory' is actually, in fact, operating successfully in service to that goal or not. Then he could be encouraged to consider different ways of finding 'common ground' with his loved ones (they probably want to be safe, too...they just probably don't buy into the specific 'conspiracy theory' type belief that the client happens to be preoccupied with).