I've never publicly said this before, but I had this experience with Donald Knuth - I emailed asking him for copyright permission for something on Wikipedia, and he gave it (public domain), but he was extremely nasty about it because I had to reply asking for clarification and apparently receiving an email was extremely disruptive to him.
I try not to talk to public figures, most of them are only nice when in the context of what they are trying to sell. The rare exceptions deserve the praise they get.
I don't even know why I'm writing this......... it was years ago.