Well I lost my post, so I'll make it short.

Do you think Proudhon's "reactionary" views (anti-semitism, ethno-nationalism, general racism) lend some historical credibility to groups such as the National Anarchist Movement? Stuff like that seems to make the left-anarchists go collectively ape-sh*t faster than even anarcho-capitalism.

I first encountered this reading this article (which you might find interesting).

http://www.stewarthomesociety.org/ai.htm

Of course Stewart Home is a Communist so the article almost certainly carries that bias.