It is difficult to place all the blame on Renfrew, for his editor should have noticed the lack of coherence.
( It ( ( ( ( is ( difficult ( to ( ( place ( all ( the blame ) ) ) ( on Renfrew ) ) ) ) ) , ) ( for ( ( his editor ) ( should ( have ( noticed ( ( the lack ) ( of coherence ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (ADJP (JJ difficult) (S (VP (TO to) (VP (VB place) (NP (PDT all) (DT the) (NN blame)) (PP (IN on) (NP (NNP Renfrew))))))) (, ,) (SBAR (IN for) (S (NP (PRP$ his) (NN editor)) (VP (MD should) (VP (VB have) (VP (VBN noticed) (NP (NP (DT the) (NN lack)) (PP (IN of) (NP (NN coherence)))))))))) (. .)))
It's hard to completely blame Renfrew. 
( It ( ( 's ( hard ( to ( completely ( blame Renfrew ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ 's) (ADJP (JJ hard) (S (VP (TO to) (VP (ADVP (RB completely)) (VB blame) (NP (NNP Renfrew))))))) (. .)))