Just because a demon shelters some villagers does not mean it is a good demon; it may have simply kept them as its reserve food supply.
Karma is the most straightforward criterion to determine whether a living being is evil.
Anyone entangled with karma is basically not a good person; most are heinous, with very few exceptions. The most representative figure among them is the Ming River Sect Master who became a Supreme.
The Blood Sea is the most filthy place in the world, but within the Blood Sea, there is a top-grade Innate Spiritual Treasure called the Karma Fire Red Lotus.
This treasure automatically absorbs worldly karma, using it as nourishment to enhance its own power. Naturally, the Ming River Sect Master, who acquired this treasure, became entangled with karma all over.
