by those on both sides of the issues , if only for the perspective it offers 
(ROOT (S (PP (IN by) (NP (NP (DT those)) (PP (IN on) (NP (NP (DT both) (NNS sides)) (PP (IN of) (NP (DT the) (NNS issues))))))) (, ,) (PP (CONJP (IN if) (RB only)) (IN for) (NP (NP (DT the) (NN perspective)) (SBAR (S (NP (PRP it)) (VP (VBZ offers))))))))
(ROOT (S (PP (IN ) (NP (NP (DT )) (PP (IN ) (NP (NP (DT ) (NNS )) (PP (IN ) (NP (DT ) (NNS ))))))) (, ) (PP (CONJP (IN ) (RB )) (IN ) (NP (NP (DT ) (NN )) (SBAR (S (NP (PRP )) (VP (VBZ ))))))))