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:
Did they actually teach witchcraft, or esoteric Christianity? Groups who taught of the spiritual gifts of Christianity have been persecuted throughout history. They were tortured, etc. This drove them underground to safeguard the Truth of Christianity.
Satanic groups calling themselves Christians have hidden this knowledge. This knowledge is what the world needs now. Fearing it is to play into their hands.
Esoteric Christianity is not Christianity. Those groups that you mentioned were persecuted because they taught “spiritualistic” practices that are not taught in Scripture, and 99% of the time this leads to Gnosticism, contact with demons, or general heresy.
The Bible contains everything you need regarding spiritual warfare. Appealing to external esoteric teachings is only going to bring trouble.
Everything in the Bible is esoteric. How do you think John saw what he saw?
Do you think you're not in contact with demons? Spirits interact with everyone and everything. Some people choose to be conscious of this and to face their demons.
The Bible is a very mysterious book. It teaches much more than people realize. You can't appeal to the Bible to back up your points without citing particular verses. Each verse can be taken many ways.
Spiritual does not equal esoteric
Esoteric definition: intended for or likely to be understood by only a small number of people with a specialized knowledge or interest.
The Bible is written so as to be easily understood by its readers. Sometimes some of the prophetic books are initially confusing, but applying common sense and letting the Bible interpret itself will bring understanding. It’s not written to confuse people, and it’s not written to be only decipherable by clergy.
John saw what he saw because it was revealed to him by God, not because he followed occult traditions of men. Spirits might interact with humans, but it is difficult to ascertain to what extent. And I have no contact with demons because I have the Holy Spirit in me and I, to the best of my ability, eschew sin and follow Christ.
The Bible does contain a lot more than most realize, but that is due to lack of familiarity and diligent study, not due to the Bible having hidden messages or codes. As for each verse being taken many ways:
“We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts: knowing this first, that no prophecy of the scripture is of any private interpretation. For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.” 2 Peter 1:19-21 KJV
People disagree endlessly about Bible verses. If you think one party has the true meaning and all others are incorrect, then it would make sense for you to think there's nothing esoteric about it.
But personally, I can open the Bible to any page and put my finger just about anywhere and find a line that I'm not confident that I understand. Many people have studied it diligently their whole lives and still have unanswered questions. Why? Because it's definitively esoteric.
You mention heresy. It appears once in the KJV.
"But this I confess unto thee, that after the way which they call heresy, so worship I the God of my fathers, believing all things which are written in the law and in the prophets..."
This is not the only mention of heresy in the Bible.
“But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction.” 2 Peter 2:1 KJV
And the passage you quote is Paul defending himself before Felix, where Paul is saying that the Jews consider him a heretic because Paul asserts the divinity of Christ and His bodily resurrection. Jews thinking that you’re a heretic doesn’t mean anything.
Has a Christian ever falsely accused someone of heresy? Jew, Christian or other, no man's testimony of heresy is of any value.