I view any type of fundamentalism as a deterioration of moral values
While I am no fan of religeous fundamentalism, I don't think it necessarily causes a deterioration of moral values in an of itself.
I think fundamentalism causes moral stagnation, often with no rhymn or reason to their stead fast rulings.
So, for example, as we as a society move forward on issues of sexuality - the fundamentalists won't budge an inch.
But their view point isn't adding to the amount of immorality, it's just unwilling to be swayed.
However, one thing that fundamentalism does breed is this culture of non-thinking sheep willing to believe anything they are told and follow any instruction no matter how absurd.
That sort of blind obedience necessarily creates leaders who's absolute power and "moral authority" quickly become corrupt.
In that way fundamentalism enables individuals who are themselves ruthlessly immoral.