A New Plague... Metaphor for Religious Fundamentalism

Big Daddy Joel writes at TPM Cafe on religious fundamentalism as a plague. ...

Big Daddy writes:

Another epidemic, rising from the swamps of from ignorance, is upon us. A threat that kills, maims and threatens life as we know it on this planet. It’s fundamental religion. It is spreading throughout the world with impunity. The threat is most obvious in the Middle East where people murder each other in the most brutal ways.

The plague is upon us here in the United States and even a more insidious form: Christian Fundamentalism.

While agreeing with the sentiment here, I wonder what people would think if Big Daddy used this metaphor for a particular religion: Judaism for example. That brings back memories of Nazi propaganda. So why is it okay to use the metaphor for "fundamentalism"?

To use such metaphors is very dangerous, if only because it compares disease, a biological process with a cultural phenomenon.