Bleach is not any different than the liquid chlorine that the pool stores sell. There is nothing that is added to the pucks that make the chlorine in them 'liner safe'.

If it were true, everyone that uses bleach or liquid chlorine would be replacing their liners all of the time because of it.

Not sure how to argue it with him. If he believes that he is right no matter what, then it will just be a battle that probably isn't worth having.