Recently, Nobel Laureate Professor Brian Josephson was invited to a physics workshop at the Towler Institute to discuss a particular approach to quantum mechanics. Then, all of a sudden, he was disinvited. The reason? Prof. Josephson is interested in the paranormal.

Dear Prof. Josephson,

I am very sorry to have to inform you that, at my initiative, Mike
Towler and I are withdrawing our invitation for you to attend our
workshop at The Towler Institute this summer.

It has come to my attention that one of your principal research
interests is the paranormal. I have told Dr Towler that, in my view,
it would not be appropriate for someone with such research interests
to attend a scientific conference. On this basis, I have urged him to
agree to withdrawing the invitation, much to his personal regret.

I do wish I had noticed this earlier, the oversight is entirely my fault.

Nothing personal, of course. It is a purely intellectual matter.

We are very sorry for any inconvenience caused, and wish you a pleasant summer.

Personally, I would have replied along the lines of "Dear Mr. Valentini. It has come to my attention that you are an ass. Please accept my regrets for not attending. Nothing personal, of course. It is a purely intellectual matter."