Nobody is denying Rayleigh saved Hancock. What you smartasses are denying is Blackbeard being afraid of Boa. He got her by a surprise attack, and was scared to let go cause he knew she would've destroyed him and the marines if he let go of her.
So you need to use your brains here.
Rayleigh came in, and told Hancock to undo everyone. Which was a positive for Blackbeard as he could keep two of his commanders. If he had tried to fight em, the dude would've been turned into stone.