I find arguments for the nonexistence of the Invisible Pink Unicorn unconvincing also. However I’m rather short on the important thing, arguments for her existence. (Besides pineapple pizza, that is.)
Got something better for demons?
This is threadshitting.
A question challenging the source of the beliefs expressed in the context that such beliefs are contradicted by the traditions regarding demons in Ancient Greek, Muslim, Japanese, or other cultures that expressed a belief in demons is legitimate.
A simple denial that such beings exist or an attempt to perform long-distance psych evals on the poster are not appropriate to this discussion.
[ /Moderating ]
So is a pentagram bigger or smaller than a kilogram?
We cannot always trust our senses, it’s certainly not uncommon to see and hear things which aren’t there or to misinterpret something as preternatural when in fact there’s a perfectly logical explanation.
It is upon the believers to show evidence for the existence of demons, not the other way around. If one believes hard enough, any evidence to the contrary can be explained away and/or denied. When it comes to belief in demons and the like, one of the problems is that any evidence can be(and very often has through the centuries) dismissed as false evidence-tools of some evil entity.
Understood.
Literally before we can go any further in this discussion, we must define what we mean by the term “demon”. I can’t even tell you if I believe in demons or not unless I know what you mean by that term. And many of the OP’s questions would be answered immediately by a proper definition.
So do I. My demons tell me that your demons don’t exist.
To the OP: how do you know it was a demon and not a ghost, fairy, jinn or kami?
Can you seriously not extrapolate from the OP what kind of demons he is talking about?
Hint: It’s not the figurative or metaphorical kind.
To the OP: how can you be certain you were speaking to supernatural beings, as opposed to either a hallucination or someone playing a trick on you?
I can figure out some of what he’s talking about. But not enough. For instance, in some conceptions, angels and demons are the same inherent sort of entities, but angels are, by definition, entities of that sort that do good, and demons are, by definition, entities of that sort that do evil. Under that definition, it’s impossible for a demon to do good, because a demon who does good isn’t a demon any more. Other conceptions might allow for some third category of beings of the same basic sort, such that angels always do good, demons always do evil, and beings of the third type (which have a number of different names in different cultures) sometimes do good and sometimes evil. Under that conception, it’s still impossible for a demon to do good, but the entity the OP is interacting with could be one of those third-types.
Basically, the OP is claiming to be interacting with an entity. She further claims that the entity she is interacts with is a demon. What does she mean, by identifying him as such?
I would be very surprised if the OP is not a she.
The OP also claims to have spoken with the Archangel Michael and to possess (as of yet unnamed) psychic abilities. In my opinion, that’s just too much claiming to take at face value, and the OP really needs to start backing up these fantastic claims.
When I saw your xkcd link I assumed it would be to this one: xkcd: The Economic Argument. I assumed wrongly.
I’m sure controlling (or even influencing) a platoon of demons would be highly profitable. Nobody’s done it. [Now that we’re in GD] Although maybe Trump comes close? 
Not true, it is still in print. You can buy copies here: https://www.amazon.com/Angels-Demons-Novel-Robert-Langdon/dp/074349346X/ref=sr_1_1?ie=UTF8&qid=1474905839&sr=8-1&keywords=angels+and+demons+book
Have we figured out yet why there might be demons who don’t do whatever they want?
Are some of them restricted by the Code of Demon Ethics™, or afraid of retribution by the Archangel Michael?
The OP claims not to follow any particular religion, but also claims to talk with the Archangel Michael(which could lead one to think that her/his demons are Christian-based), and on top of it all claims to have psychic powers. I’m not about to extrapolate anything from that mish-mash until the OP clarifies exactly what she/he claims is going on.
I believe some Greek philosophers, notably Socrates, used the word daimon in a largely positive sense.