Not everyone who claims to have secrets is a charlatan or fraud… but exercise caution. There are, and always will be, undesirable or immoral persons who will take advantage of relationships for their own benefit, or to feed their own ego. For your own security exercise discretion with who you trust and share your craft secrets.
In many places there is no fear of another “burning times”, but one never knows. It’s best to be in the closet if something bad were to occur. Putting yourself at risk in the blind hope that nothing terrible will happen is foolish. Although discrimination is illegal, we all know it happens. Do not open yourself up to it.
Security of self can often be reasonably assured. Security of a coven is more difficult. Ensure trust is rightly earned, and even then take “The Measure.”
Do not have qualms about holding secrets yourself. If you learn and grow, there is nothing stopping others from discovering the same knowledge on their own. You have no obligation to share what you have learned. Knowledge and wisdom will make itself known to those ready to accept it. On the other hand, there is nothing saying you cannot share it either. Remember, all actions have a reaction though… no matter how well-intentioned.