Piers, you are not invading my "cosy little world" simply exposing yours if you think it possible to "argue fascism and racism out of existence".
Fanatics of any type do not respond to reasoned argument, a salient feature of fanaticism, but only take the chance to repeat ad nauseum their insidious ideas. The chatteratti enjoy such arguing but since they are already of the same basic opinion it is rather pointless. A study of Political History of the 20Century will quickly inform you of the aims,objectives and doctrines expressed - they are well documented.
What you can do is refuse to trade with any business supporting fanatic organisations -BNP, white supremecists,etc. If you find the music in a store, complain to the management, if you hear it on radio or see it on TV, complain to the station involved and get all you friends and contacts to do the same.
If someone at work or socially expresses such views, point out that you find them abhorrent and that you will no longer work or associate with them = shun them. If you are asked by another why you have done this then you can explain and hopefully they might feel that they should do the same. It is hard for someone to maintain the arrogance needed to sustain fanatical views if they are being ignored by their peers.
In the case of David Hannam - do not reply to his postings - boycott his thread. You could also mention you are going to boycott his music label and complain about any public performance of his work or his groups.