Perhaps some pages should be banned, but I worry that it will be harder for researchers to get important (aka, dam*ing) information on some of the evildoer groups.
Some of the Islamicist sites have been helpful to me in finding interesting connections between notorious individuals, even though I haven't found anything groundbreaking. I like to know the option exists for evildoers to accidentally reveal too much about themselves. What if the public had not had access to Kaczinski's diatribe?
Especially if this is more of the "sweep it under the rug and we don't have to deal with it" mentality that Germany and France so apparently favor.
Blocking access through search engines is simply cosmetic surgery.