should be held responsible

The key to answering your question is to look at the meaning and usage of the transitive verb "hold".

"hold" = to consider that something is true (Oxford)
認為; 持有(見解等) (Yahoo)

Common usage: (Oxford)
(1) hold that… e.g. I still hold that the government's economic policies are mistaken.
(2) hold somebody/something + adjective 動詞＋受詞＋形容詞
e.g. Parents will be held responsible for their children's behaviour.
(3) be held to be something e.g. These vases are held to be the finest examples of Greek art.

"should be held" = model + verb in passive voice

2011-12-24 15:51:36 補充：
correction: modal (not model)