how to debate a fascist

Perhaps Bertrand Russell offers a good path. In 1962 Sir Oswald Mosley, founder of the British Unit of Fascists before WWII and still an active fascist, wrote to the 90 year old Russell trying to goad him into a debate.  Here's Russell's reply:

 

Dear Sir Oswald,

Thank you for your letter and for your enclosures. I have given some thought to our recent correspondence. It is always difficult to decide on how to respond to people whose ethos is so alien and, in fact, repellent to one’s own. It is not that I take exception to the general points made by you but that every ounce of my energy has been devoted to an active opposition to cruel bigotry, compulsive violence, and the sadistic persecution which has characterised the philosophy and practice of fascism.

I feel obliged to say that the emotional universes we inhabit are so distinct, and in deepest ways opposed, that nothing fruitful or sincere could ever emerge from association between us.

I should like you to understand the intensity of this conviction on my part. It is not out of any attempt to be rude that I say this but because of all that I value in human experience and human achievement.

Yours sincerely,

Bertrand Russell