Nazi blogs may be allowed. Nazi trolling of other blogs won't be. Among the features that sent Nazis to Twitter and Tumblr instead of LJ, DW and other clones: You can't reblog other people's things; you have to comment - and they can delete the comments or ban you from their blogs. They can't set up a stronghold and then go stomp on people; it's too easy for the other people to just cut them off. Blogs can block anon commenting, and can block individuals, and can set some or all of their posts to "access list only" - only the people you've chosen can see those posts.

And while I don't think DW is going to delete blogs just for being pro-Nazi, they absolutely will delete them for harassment. (Unlike Twitter, unlike Tumblr.)