Sentence:  Because he spoke openly with what Channing had prophesied someone might - with daring hyperbole - Parker vindicated Channing 's further prophecy that he who committed this infraction of taste would promptly discover how little mercy liberals <WSD>were</WSD> disposed to allow to libertarians who appeared to them libertines . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)