In terms of actually being able to affect the reproduction angle, yes, it about pointless to attack it that way.

Beating the message with a better message is the desired endstate. I was using CDs/DVDs as an example of the medium where the opposing message gets out there the quickest and across the widest target area. Jihadist websites on the internet do not make for a "the sky is falling" situation. Now, if there is communication and coordination going on through those websites, then that's a different story. Websites alone do not make for much of an IO effect in my mind.