Hee hee! I love Gordon.
He's right, of course, there's not enough understanding of the framework of the spirits of the "demonic" grimoires among the traditionalist and fundamentalist movements in the practical occult. I classify all the grimoires of the Renaissance as being, pretty much, Hermetic in fundamental nature. They are founded on the principles of the Hermetic cosmology.
Hermetics has a rich landscape of spirits. There are the Celestial spirits of the heavens, the Terrestrial spirits of Nature, Elemental spirits, and Infernal spirits from the underworld. We are related to all of them, via our parents, First Father and the Spiritus Mundi. We are kith and kin to them all.
In the grimoires, the spirits that get classified as "demons" most often (i.e. when I think about them) are the spirits of the Lemegeton's Goetia, maybe the Theurgia Goetia, the spirits of the True Grimoire, the spirits of the Testament of Solomon, and some of the spirits you run into in the Clavicles, maybe. Oh, and the demons of the Abramelin rite, which was entirely about conjuring demons for money and happiness and not at all interested in happy illumination or enlightenment. Money. Power. Influence. Happiness. That's what the Abramelin rite is about, and it's demons that get it for you.
Now Jake Stratton-Kent has gone over it in awesomely better detail in Geosophia and True Grimoire, so I'll refer you there for more information about these next bits if you have questions. I'm summarizing and possibly paraphrasing, and probably changing some stuff to make it fit. But the gist of it is that the Demons are Elemental Spirits, for the most part. The four demonic kings are the kings of the elemental Kingdoms, and everyone else is a servant of them.
That's it, folks. Most of the "demons" you hear so much about are Elementals. Bet you didn't know every time you did an Elemental Kingdom rite you were conjuring demons, eh? Well you were! You're a Goetic Magician now, man, it's all over for you. You might as well be calling up the spirits of the dead, you damned necromancers!
So anyway, not a big deal, really. Demons are elemental spirits. That's the Terrestrial realm, mostly. So why the evil reputations? Let's not blame the Christians entirely, though they can carry a great deal of the blame. If you look at elemental spirits in many cultures, it's not long before you see that they are often up to no good. Faeries and sprites, leprechauns and dragons, the interactions between the two rarely end well. They have a reputation for mischief, the painful kind, disease-spreading, and strife-causing.
Now nature spirits are worker bees, just like the planetary governors of the allegedly celestial spheres. They are the Intelligences of the forces that oversee. They create reality, like blue-collar workers. They can be crass, opinionated, and bitter. They can also be the intelligences of disease, overseeing the manifestation of the common cold, or cancer. They are the spirits responsible for creating the things that come from nature that we don't like as much as the things that we do like.
So when they aren't in the circle or triangle, they are off overseeing the things over which they rule. They have legions of helpers because think about how many forces are interacting at once to maintain this universe. Legions and legions. And we can tap their forces if we want, but it's not guaranteed to be any entity who likes you, and you can't expect not to be impacted by what they are also lords over. Like if you conjure a apirit known to be a liar, don't be surprised if you, even though you've bound the spirit to tell the truth, become a liar yourself for a bit after working with him. They rub off on us.
It's no big deal, they aren't "bad." They just manifest things we don't like. You have to be really careful to understand the nature of the spirit you're working with when you do material magic so you can understand how it will manifest your results.
But on the other hand, these spirits are wicked smart when it comes to learning how to manifest things ourselves. They can teach us the nature of things, the correspondences of different elements, and how to combine them in neat ways to create specific results in our magical activities. We can get serious skills in mastering the manifestation game from them, if we ask for learning, teaching, education, information, skill, and talent in the spheres they rule. They can teach us how to "phrase" things when we speak them into existence.
And when they're done with us, they go back to their business, manifesting whatever needs manifesting wherever it's necessary. They aren't planning anything evil (except the one who are supposed to, and still... "evil"), they aren't riding politicos (except the ones who do) or running multi-generational experiments on human genetics (except ... well... it's a secret...).
So no need to worry about those demons and whatever they might be up to when they aren't around.
Everything's just fine.