If you are asking how to refute arguments presented by someone else, the answer is you can’t. Illuminati symbology is practically everywhere that’s “important” in western society. If you want to see a lot of it in one place, browse vigilantcitizen.com (although to me that site is less potent now than it used to be). Whether the symbology presented at this level is backed by any measure of control over the world is another question, but you really can’t refute that there are plenty of symbols.
Separately (or together) there are hidden or not so well hidden efforts to control various aspects of the planet at whatever macro level, and you can find those by looking for them. Confession of an Economic Hitman author John Perkins defuses the term “conspiracies” by calling them “a fraternity of ideas” (for which third world leaders can find themselves assassinated or their countries invaded, by the way) and states “Some would blame our current problems on an organized conspiracy. I wish it were so simple. Members of a conspiracy can be rooted out and brought to justice. This system, however, is fueled by something far more dangerous than conspiracy. It is driven not by a small band of men but by a concept that has become accepted as gospel: the idea that all economic growth benefits humankind and that the greater the growth, the more widespread the benefits. This belief also had a corollary: that those people who excel at stoking the fires of economic growth should be exalted and rewarded, while those born at the fringes are available for exploitation.”
Whether (1) the symbology and (2) the attempts to control anything are married to each other is debatable, but it’s not a stretch to say they both exist separately.
A third consideration might be “so what?” because a question often given short shrift by a conspiracy theorist is how much does this affect your life really? One might say “all of it” because it seems so pervasive in the world and even in the products we consume. This is actually a pretty reasonable response because the rabbit hole, in my experience, is bottomless, and when you start down the path of looking at this stuff, it’s like everything you thought you knew, all of history especially, has to be relearned.
It may create in that person some kind of “prepper” impulse (I’m using “prepper” as a catch-all for any kind of resistance to perceived threats from perceived conspiracies), but ultimately that kind of effort is pretty difficult. So it may be worthwhile for you as a “sane” person to just point this out from time to time—that life is still pretty good.
For me, someone who went as far down the rabbit hole as I could manage, it actually helped lead to a blessing, which has been a spiritual enlightenment of sorts. By engaging with all of that so thoroughly, my sense of reality got really malleable, and that opened my mind to some other possibilities related to our spiritual nature, and I feel a greater sense of peace and “all-right-ness” than I ever have.
I think one key in this was having the luxury of time that I did to be so thorough in my seeking. In other words, I got all the way to the end of it instead of dabbling enough to just satisfy my taste for fear.
Actually, that might be another tack—getting your conspiracy theorist to self-inquire about whether he or she is dosing on fear. I certainly was.