i would doubt that 4lb line can cause as much damage as 8lb braid, because the braid could be thinner, and the pressure put on the braid can be a lot more.
but i have never seen damaged mouths due to braid, especially by hooklength braids i.e kryston range, but definately can imagine it happening as braids get thinner and stronger.
Howard, more information would be good, lots of things damage fish and its normally not the product but the way it is used.
Ask them.
In what way is Braid to blame?
What evidence do they have?
Have they thought about the problem being caused by something else?
Braid is used to such a high pecentage for hook links I can only assume that the club know something that the rest of us don't, if they do then it would be in everyones interest if they made this information available to all.