I agree that, in the end, it is true that this person was a troublemaker that should not have been invited in the first place. However, it seems from the text that the organizers decided to cancel the invitation before receiving any input whatsoever from the concerned person. I cannot see how this is ok.
Imagine that this person has been bullied in such a way out of a dozen conferences by a concerted effort of a few colleagues that hate her. And for this last conference, she exploded with great and not completely unjustified ire. Whatever, it is a bit absurd to have an opinion on this question without information from both sides.