I was taught that but and the adverb showing contrasting ideas ,such as nontheless, nevertheless and the like, should not be used in the same sentence because it tends to make the sentence redundant.
However, I found the sentence like the one below very frequently:
We should be thankful that Osama bin Laden's intervention in our election took the form of a videotape, and not an attack, as in Madrid on March 11. But it was an attempted intervention nonetheless.
What should be the rule that the usage of "but...nonetheless" is juistified?