You are being abused. You have the right to your opinion. You have the right to express your opinion. Anyone who tries to tell you otherwise or punishes you for your free expressions is abusive.
Ask them if what you posted was true or false. You know it's true. They know it's true. Why are they so afraid of other people knowing the truth about what they believe?? Don't let them get away with saying it was "disrespectful" - it's the truth. It is what it is, there's no disrespect in truth. Perhaps they cannot tolerate having the truth about them known on a public forum such as Facebook.
I wouldn't have deleted my Facebook account over them. I would have unfriended or blocked them instead, so you can be free to speak your opinion without reprisal.
And one other thing - I would cancel the Bible Study™ with the Elder™ and his Pioneer™ wife. There needs to be some consequences for the way they are mistreating you.