Sentence:  At the same time, Mr. Irons said, it is important to separate “this very valiant and completely kosher and clean repository of public material, which we perfectly endorse, and this kind of <WSD>firebrand</WSD> ‘We want to show the publishers they're wrong' kind of attitude.” 
Meaning of the word marked with <WSD> tags:  An argumentative troublemaker or revolutionary; one who agitates against the current situation.