Educate yourselves (this is not mine):
Idolatry consists of endless rituals associated with superstitions, magic and mythical beliefs. “Death” was always considered the most terrifying mystery, and it triggered extreme anxiety and agitation. Dead people, their invisible spirits, were often the object of fear, reverence and especially of worship. Halloween is not an exception. “All-hallow-even” celebrates the “day of all (dead) saints”.
The ancient Celts celebrated Halloween at the end of summer, because they believed that the evil spirits and the souls of the dead were visiting the world of the living at that time. The pagans considered the dead more or less as Hollywood considers the “zombies”: bad and dangerous. The dead returned to this world angry, vengeful and with the desire to recruit new members. The pumpkins, which resembled the disfigured faces of the dead, were carved to welcome them and appease their spirits. Great bonfires were also lit to illuminate and thus help the dead finding their way into the world of the living. Food, particularly sweets, was left outside the doors to feed the ghosts. All these favors for the dead were made out of self interest: people believed that those who did help the spirits of the dead would not be disturbed by them (“If I pacify them, they will not take me with them”).
Cats were especially important on Halloween because people believed that cats could smell and warn about the presence of invisible bad spirits. However, black cats were avoided (or killed) because witches or evil spirits reincarnated in black cats.
The devil appeared on Halloween night from hell itself. The Druids, the Celtic priests, wore masks to make the dead believe that they were one of them. These priests knocked on the doors to claim human sacrifices for the devil, or to satisfy the vengeful spirits. And if one did not want to become a human sacrifice, at least, had to appease the evil spirits with sweets.
When ehrlich yidden insist that you SHOULD give out candies then this is a truly a curse.
I shudder at the thought that Moshe Rabbienu imagined eirlich yidden handing out candies on Halloween when he warned:
וֶהֱפִֽיצְךָ֤ יְהוָה֙ בְּכָל־הָ֣עַמִּ֔ים מִקְצֵ֥ה הָאָ֖רֶץ וְעַד־קְצֵ֣ה הָאָ֑רֶץ וְעָבַ֨דְתָּ שָּׁ֜ם אֱלֹהִ֣ים אֲחֵרִ֗ים אֲשֶׁ֧ר לֹא־יָדַ֛עְתָּ אַתָּ֥ה וַאֲבֹתֶ֖יךָ עֵ֥ץ וָאָֽבֶן׃
(See, Rashi’s question there and Alshick there and Abarbanel on Devarim 4:25:2)