I just think the criteria of what makes it Satanic to you is whether or not it was written in the Satanic Bible, which is the source of the phrase "Satanic Holidays". I find this amusing.
Valborg's Night was the witches's night where they had sex with the devil and it was the night before Beltane which is associated with fertility. Halloween is said to be the night where devils and demons are out. I don't find it amusing that LaVey selected these holidays.
You'd argue the spin of a fermion to a CERN physicist. Even I wouldn't do that.
The Satanism of it all explained.
Originally it was called Beltane, this was a pagan celebration of the beginning of summer (not spring, I confused it with Ostera in a previous post). Beltane later became May Day Celebrations, those still exist.
There was also a Saint named Walpurgis, who was synonymous with being an icon of protection AGAINST WITCHCRAFT after cannonization. Walpurgisnaught was a night (for this saint) to ward off evil witches and their evil beliefs. It and all its variations on April 30th didn't exist until Christians used it to subvert a concurrent pagan holiday.
The purpose was a psycholoigical cultural appropriation of those wicked pagans LITERALLY DANCING AROUND THE MAY POLE. That's the origin, pagans doing jesus-less dances and a fear of dark forces associated with that.
To demonize PAGANS, and their wicked spring/summer celebration, this night was created. Witches are just stronger on their Sabbats.
Fast forward thousands of years and the "Satanic" celebration is IRONIC. Its celebrating THE OPPOSITE of the intent of the anglo-saxon Walpurgisnaught.
I mean, you can go out pretending to fornicate with demons, but it's not like its satanic association is anything more than a religious satire of the christianization of pagan tradition.
What better night to suspend any magical disbelief? Take that Walpurgis, Yay Satan!
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Homework, so you stop looking so retarded.
Study this ancient chart for the origins of these 'Satanic' Holidays.

[The Eight Witches Sabbats]
** many edits.