David Gerard wrote:
perverted-justice.com is redirecting all hits referred from Wikipedia to an attack page. Nevertheless they're notable and their URL should be in their article.
I wasn't aware of this. However, this is a people problem at the remote website, not a technical problem for Wikipedia. The obvious solution would be to redefine Template:Derefer so it puts <nowiki> around the remote URL, rather than linking.
There are many other websites where you cannot create deep links at all. For example you cannot link to information about a book at the Library of Congress catalog website. This too is a people problem at the remote site (because enabling deep links isn't really rocket science). So, you just don't link there.