I wasn't familiar with "Chatham House rules". But it is allows members to present controversial arguments but prevents anyone from associating their arguments to them after the fact. For example, I can cite the argument later but not say who made the argument in order to prevent them from political repercussions. https://en.m.wikipedia.org/wiki/Chatham_House_Rule

Certainly very weird that the environment was that charged politically that these rules were needed.