Q: Jehovah's Witnesses claim that it's volunteer to be a Jehovah's Witness. NO!! It's Not volunteer. They use manipulations towards their family members who refuses join their cult.

Does this sound natural?
A: something like:
Jehovah's Witnesses claim that being a Jehovah's Witness is completely voluntary. NO!! It's not voluntary. They manipulate family members who refuse to join their cult.
Q: The Jehovah's Witnesses teachings and believes are damaging / harmful / detrimental for families on so many levels.

Which word choice would be good here?

The Jehovah’s Witnesses’ teachings and BELIEFS are MANIPULATIVE towards families on so many levels.
Q:Jehovah's Witnesses worship their sect instead of worshiping God - the Creator.
✓ The Jehovah's Witnesses teachings and activities are aimed to destroy the value system of a person who has become their victim, the victim of their toxic propaganda.
✓ The Jehovah's Witnesses substitute family values, societal values ​​for a blind adherence and obedience to the instructions of their criminal group.

✓ All of the mentioned above is done in an organized and professional manner.
Does this sound natural?
A: It's not a very good argument to say that Jehovah's Witnesses worship something other than their god. Many of their practices are specifically designed to avoid the accidental worship of anything other than God. For example, they refuse to celebrate any holidays, even Christmas, because of its origins as a pre-Christian celebration.

There are plenty of real things you can criticize Jehovah's Witnesses for. You don't need to resort to lies and unsupported arguments. For example, children who break the rules of their church may be "disfellowshipped" and shunned by their families, and the church's ban on blood transfusions has surely caused multiple deaths.
Q: Jehovah Witnesses の発音を音声で教えてください。
Q: Jehovah's Witnesses believers reject the transfusion even if that is fatal. この表現は自然ですか?
A: It’s mostly natural, but somewhat ambiguous at the end. Also, it’s not grammatically correct to say “__(religious demonym)__ believers” (instead of “Catholics believers” or “Muslims believers” it’s just “Catholics” and “Muslims”). I would have said “Jehovah's Witnesses reject blood transfusion, even if the consequences will be fatal.”