It means that they gather and interpret their material fairly and argue about its interpretations rationally.
( It ( ( means ( that ( they ( ( ( ( ( ( gather and ) interpret ) ( their material ) ) fairly ) and ) ( ( argue ( about ( its interpretations ) ) ) rationally ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ means) (SBAR (IN that) (S (NP (PRP they)) (VP (VP (VB gather) (CC and) (VB interpret) (NP (PRP$ their) (NN material)) (ADVP (RB fairly))) (CC and) (VP (VB argue) (PP (IN about) (NP (PRP$ its) (NNS interpretations))) (ADVP (RB rationally))))))) (. .)))
The judge gathers and interprets material fairly and argues about it rationally.
( ( The judge ) ( ( ( ( ( ( gathers and ) interprets ) ( material fairly ) ) and ) ( argues ( ( about it ) rationally ) ) ) . ) )
(ROOT (S (NP (DT The) (NN judge)) (VP (VP (VBZ gathers) (CC and) (VBZ interprets) (NP (NN material) (RB fairly))) (CC and) (VP (VBZ argues) (PP (IN about) (NP (PRP it)) (ADVP (RB rationally))))) (. .)))