Sentence:  Not only , as we know , did Chou En-lai publicly treat Khrushchev 's attack on Albania as `` something that we cannot consider as a serious Marxist-Leninist approach '' to the problem ( i. e. , as something thoroughly dictatorial and `` undemocratic '' ) , but the Albanian leaders went out of their way to <WSD>be</WSD> openly abusive to Khrushchev , calling him a liar , a bully , and so on . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)