Contrary to popular belief, Demons do not have insatiable and uncontrollable bloodlust. Although they consume human flesh they are not wild animals.
Much as any person could walk into a market and peruse the food there, even while hungry, so too can Demons mingle with humanity.
Thankfully there are very few Demons at any moment in our world. This has less to do with Humanities ability to repulse them, and more to do with the very tight restrictions the Demonic Masters maintain.
Demons in our world tend to grow stronger much faster than a Demon in the Demonic Planes, and it is theorized that the Demonic Masters do not wish any to grow too strong, without their oversight.
There is also "The Guardian", a mythical being that is supposed to oversee the barrier between our world and that of the Demons. The legends do not mention how many Demons would have to cross over to trigger some kind of protective action, but it is very clear that the Masters at least view this being as real.
Still, if you are to encounter a Demon, understand that they DO view you as food, simply food that they can hold a conversation with.
-Writings on "Commonly held misunderstandings of the vile and terrible beings known as Demons", a forbidden text