Answer:
WE CAN HELP PEOPLE BY DOING THEIR TASK AND HELPING THEN
As you said above, the word "bob" means fencing and you want to know how this can have a double meaning related to homophobes.
This is what I see the 2 meanings as:
1. fencing, as in taking out your fencing sword
2. take out your penis, as penis would be another word for sword in plays/books such as the one you're reading - this would be relating to gays if the convo was btwn 2 men
The main idea of the passage above from Cotton Mather's "The Wonders of the Invisible World" is to justify the outcome of the trials. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.