This letter makes perfect sense to me if he had sent it as his first reply to a fascist in 1946. Why did he correspond with him over 43 previous letters from 1946 and only in 1962 act as though he had principled objections to corresponding with fascists? The tone is not "this time you've gone too far", or "I have decided we're not getting anywhere", but "We have nothing in common and could never converse". I wonder if he realized it was the same guy, or was submitting this to some public forum.