Freemasonry is a secret society.
All secret societies are satanic.
Freemasonry is the most well known secret society.
Freemasonry itself is a satanic organization, even if some of the Freemasons seem otherwise like "good guys."
Here is an overview of Freemasonry:
Secret Societies aren't inherently Satanic, but they are predisposed to fall to Satanism.
Anything done in secret eventually gets taken over by Evil in secret. With no one having the knowledge to stop the corruption, how could you possibly hope to persist when so many wish to take over your organization and steer it off a cliff?
No... Secret Societies aren't Evil by nature, just like driving your car backwards isn't necessarily Evil. Sure, you might be able to get away with it for a while, and you might even be good at it, but eventually you'll crash ass-backwards.
If what you do has to be obscured from the masses, no matter if it is honestly altruistic or not, you're just begging for Satan to come along and take advantage of your pride.
As for Freemasonry in particular... All Secret Societies espouse the Hidden Truth of the world, otherwise people wouldn't see enough value to bother joining and doing all the weird rituals to begin with. They do, however, eventually pervert the Truth with lies and take advantage of the trust they build with their members.
TL;DR: Secret Societies don't have Checks and Balances because they are secretive. Therefore, they will always be completely vulnerable to corruption from within, and have no backing from The People to weed out said corruption.
Long ago, I joined Rosicrucians by mail. Their booklets taught witchcraft, even before I knew what witchcraft was. I stopped and threw the booklets in the garbage. It is not something to be messed with.
Did it teach spells (curses on people or rituals for favors) specifically, or were they just symbolic mumbo-jumbo?
I saw some AMORC (Rosicrucian) neophyte manuals and it was excercises to develop aura seeing ability and communicating with the mind amongst other things