"There are many kinds of whores...some of them take money to get naked...others just sell out their friends (and anyone else handy) for cheap short term gain... frankly, the naked-getting ones seem less objectionable...better value for money..."
I'm going to strive to be nice, and not mention names. A week is plenty of notice to any competent person to find a substitute speaker, guest, or host. It takes some real gall to ask someone who has spent months being ignored, talked over, and patronized - and STILL takes the classy way out - to come back and play substitute for the primary offender.
To then, when the classy person just can't bring his/herself to betray his/her principals and further enable the misbehaving sort, rush out and publicly deride said individual goes beyond gall, right into the land of the vile.
Myself...once certain boundaries have been crossed, I find it best to simply eject sufficiently objectionable persons from my life, shunning them with some vigor, as they are simply not worth the time, high blood pressure, or irritation that EITHER playing nice with them for the sake of politeness requires...or the effort required to truly show ones depth of dismay with such creatures.
Malice clearly would tend to qualify, but I argue that narcissism combined with being hurtful to someone I consider a friend and worthy intellectual playmate qualifies such a person for shunning...and that continued acknowledgement of their existence in all but the most indirect terms (unless it's for cheap laughs, of course...and even that should probably be avoided as "too easy") will probably only irritate me, and merely serve to lengthen the period of time required for the objectionable one (if capable) to achieve sufficient personal growth as to become a worthwhile conversationalist.