i see no reason it would. If there was at least one person in that prison capable of blocking him with armament haki, he wouldn't be anywhere near as invincible to the prisoners as he is.
I would guess it depends on the haki and the person using it. I would say as a blanket statement no haki wouldn't automatically equate to being able to block Magellans poison, Magellans' a strong character I would assume you'd already need to be right around his level
I think Armament would only block the touch poisoning, but things like hydra and similar attacks, that's end game...
Because BB was also bathed in the poison, but he couldn't use his Yami-neutralizer because once left Magellan's body, it's regular poison not a DF thing anymore.